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Cyclopedia 


V 

Engineering 


A  General  Reference  Work  on 

STEAM   BOILERS,    PUMPS,    ENGINES,    AND    TURBINES,    GAS    AND    OIL    ENGINES, 
AUTOMOBILES,     MARINE    AND    LOCOMOTIVE    WORK,    HEATING    AND 
VENTILATING,  COMPRESSED  AIR,   REFRIGERATION,   DY- 
NAMOS,  MOTORS,  ELECTRIC  WIRING,    ELEC- 
TRIC LIGHTING,  ELEVATORS,  ETC. 


Editor-in-Chief 
LOUIS  DERR,  M.  A.,  S.  B. 

PROFESSOR  OF   PHYSICS,    MASSACHUSETTS   INSTITUTE   OF   TECHNOLOGY 


Assisted  by  a  Staff  of 

CONSULTING  ENGINEERS,    TECHNICAL   EXPERTS,    AND   DESIGNERS   OF  THE 
HIGHEST   PROFESSIONAL  STANDING 


"with  QIWX  -fiup^  Thousand  Engravings^ 


SEVEN     VOLUMES 


CHICAGO 

AMERICAN   TECHNICAL  SOCIETY 
1910 


51909       B--e..- 


COPYRIGHT,  1902,  1903,  1904,  1906,  1907,  1909 

BY 

AMERICAN  SCHOOL  OF  CORRESPONDENCE 


COPYRIGHT,  1902,  1903, 1904.  1906,  1907.  1909 
BY 

AMERICAN  TECHNICAL  SOCIETY 


Entered  at  Stationers'  Hall  London 
All  Rignts  Reserved 


<J 


o 

Editor-in-Chief 
LOUIS   DERR,  M.  A.,  S.  B. 

Professor  of  Physics,  Massachusetts  Institute  of  Technology 


Authors   and   Collaborators 

LIONEL  S.  MARKS,  S.  B.,  M.  M.  E, 

Assistant  Professor  of  Mechanical  Engineering,  Harvard  University 
"1  American  Society  of  Mechanical  Engineers 


LLEWELLYN  V.  LUDY,  M.  E. 

Professor  of  Mechanical  Engineering,  Purdue  University 
American  Society  of  Mechanical  Engineers 


LUCIUS  I.  W1GHTMAN,  E.  E. 

Electrical  and  Mechanical  Engineer,  Ingersoll-Rand  Co.,  New  York 


FRANCIS  B.  CROCKER,  E.  M.,  Ph.  D. 

Head  of  Department  of  Electrical  Engineering,  Columbia  University,  New  York 
Past  President,  American  Institute  of  Electrical  Engineers 


CHARLES  L.  GRIFFIN,  S.  B. 

Assistant  Engineer,  the  Sol vay- Process  Co. 
American  Society  of  Mechanical  Engineers 


VICTOR  C.  ALDERSON,  D.  Sc. 

President,  Colorado  School  of  Mines 

Formerly  Dean,  Armour  Institute  of  Technology 


WALTER  S.  LELAND,  S.  B. 

Assistant  Professor  of  Naval  Architecture,  Massachusetts  Institute  of  Technology 
American  Society  of  Naval  Architects  and  Marine  Engineers 


Authors  and  Collaborators— Continued 


CHARLES  L.  HUBBARD,  S.  B.,  M.  E. 

Consulting  Engineer  on  Heating,  Ventilating,  Lighting,  and  Power 


ARTHUR  L.  RICE,  M.  M.  E. 

Editor,  The  Practical  Engineer 


WALTER  B.  SNOW,  S.  B. 

Formerly  Mechanical  Engineer,  B.  F.  Sturtevant  Co. 
American  Society  of  Mechanical  Engineers 


HUGO  DIEMER,  M.  E. 

Professor  of  Mechanical  Engineering,  Pennsylvania  State  College 
American  Society  of  Mechanical  Engineers 


SAMUEL  S.  WYER,  M.  E. 

American  Society  of  Mechanical  Engineers 
Author  of  "Gas-Producers  and  Producer  Gas" 


WILLIAM  G.  SNOW,  S.  B. 

Steam  Heating  Specialist 

American  Society  of  Mechanical  Engineers 


GLENN  M.  HOBBS,  Ph.  D. 

Secretary,  American  School  of  Correspondence 
Formerly  Instructor  in  Physics,  University  of  Chicag 
American  Physical  Society 


LOUIS  DERR,  M.  A.,  S.  B. 

Professor  of  Physics,  Massachusetts  Institute  of  Technology 


JOHN  H.  JALLINGS 

Mechanical  Engineer  and  Elevator  Expert 


HOWARD  MONROE  RAYMOND,  B.  S. 

Dean  of  Engineering,  and  Professor  of  Physics.  Armour  Institute  of  Technology 


Authors  and  Collaborators — Continued 


WILLIAM  T.  McCLEMENT,  A.  M.,  D.  Sc. 

Head  of  Department  of  Botany,  Queen's  University,  Kingston,  Canada 


GEORGE  C.  SHAAD,  E.  E. 

Head  of  Department  of  Electrical  Engineering,  University  of  Kansas 


GEORGE  L.  FOWLER,  A.  B.,  M.  E. 

Consulting  Engineer 

American  Society  of  Mechanical  Engineers 


RALPH  H.  SWEETSER,  S.  B. 

Superintendent,  Columbus  Iron  &  Steel  Co. 
A  merican  Institute  of  Mining  Engineers 


CHARLES  E.  KNOX,  E.  E. 

Consulting  Electrical  Engineer 

American  Institute  of  Electrical  Engineers 


MILTON  W.  ARROWOOD 

Graduate,  United  States  Naval  Academy 

Refrigerating  and  Mechanical  Engineer,  with  the  Triumph  Ice  Machine  Company 


R.  F.  SCHUCHARDT,  B.  S. 

Testing  Engineer,  Commonwealth  Edison  Co.,  Chicago 


WILLIAM  S.  NEWELL,  S.  B. 

With  Bath  Iron  Works 

Formerly  Instructor,  Massachusetts  Institute  of  Technology 


GEORGE  F.  GEBHARDT,  M.  E.,  M.  A. 

Professor  of  Mechanical  Engineering,  Armour  Institute  of  Technology 


HARRIS  C.  TROW,  S.  B.,  Managing  Editor 

Editor-in-Chief,  Textbook  Department,  American  School  of  Correspondence 
American  Institute  of  Electrical  Engineers 


Authorities  Consulted 


THE  editors  have  freely  consulted  the  standard  technical  literature  of 
Europe   and  America  in  the  preparation  of  these  volumes.    They 
desire  to  express  their  indebtedness,  particularly  to  the  following 
eminent  authorities,  whose  well-known  treatises  should  be  in  the  library  of 
every  engineer. 

Grateful  acknowledgment  is  here  made  also  for  the  invaluable  co-opera- 
tion of  the  foremost  engineering  firms,  in  making  these  volumes  thoroughly 
representative  of  the  best  and  latest  practice  in  the  design  and  construction 
of  steam  and  electrical  machines;  also  for  the  valuable  drawings  and  data, 
suggestions,  criticisms,  and  other  courtesies. 


JAMES  AMBROSE  MOYER,  S.  B.,  A.  M. 

Member  of  The  American  Society  of  Mechanical  Engineers;  American  Institute  of  Elec- 

trical Engineers,  etc.;  Engineer,  Westinghouse,  Church,  Kerr  &  Co. 
Author  of  "The  Steam  Turbine,"  etc. 


E.  G.  CONSTANTINE 

Member  of  the  Institution  of  Mechanical  Engineers;  Associate  Member  of  the  Institu- 

tion of  Civil  Engineers. 
Author  of  "Marine  Engineers." 

*^ 

c.  w.  MACCORD,  A.  M. 

Professor  of  Mechanical  Drawing,  Stevens  Institute  of  Technology. 
Author  of  "Movement  of  Slide  Valves  by  Eccentrics." 
**• 

CECIL  H.  PEABODY,  S.  B. 

Professor  of  Marine  Engineering  and  Naval  Architecture,  Massachusetts  Institute  of 

Technology. 
Author  of   "Thermodynamics  of  the  Steam  Engine,"   "Tables  of    the  Properties    of 

Saturated  Steam,"   "Valve  Gears  to  Steam  Engines,"  etc. 


FRANCIS  BACON  CROCKER,  M.  E.,  Ph.  D. 

Head   of  Department  of  Electrical  Engineering:,  Columbia  University;  Past  President 

American  Institute  of  Electrical  Engineers. 
Author  of  "Electric  Lighting,"  "Practical  Management  of  Dynamos  and  Motors." 

%• 

SAMUEL  S.  WYER 

Mechanical  Engineer;  American  Society  of  Mechanical  Engineers. 

Author  of  "Treatise  on  Producer  Gas  and  Gas-Producers,"  "Catechism  on  Producer  Gas." 


E.  W.  ROBERTS,  M.  E. 

Member,  American  Society  of  Mechanical  Engineers. 

Author  of  "Gas-Engine  Handbook,"  "Gas  Engines  and  Their  Troubles,"  "The  Automo- 
bile Pocket-book,"  etc. 


Authorities  Consulted— Continued 


GARDNER  D.  HISCOX,  M.  E. 

Author  of  "Compressed  Air,"  "Gas,  Gasoline,  and  Oil-Engines,"  "Mechanical  Move- 
ments," "Horseless  Vehicles,  Automobiles,  and  Motor-Cycles,"  "Hydraulic  Engineer- 
ing," "Modern  Steam  Engineering,"  etc. 

r*» 
EDWARD  F.  MILLER 

Professor  of  Steam  Engineering,  Massachusetts  Institute  of  Technology. 
Author  of  "Steam  Boilers." 

ROBERT  M.  NEILSON 

Associate  Member,  Institution  of  Mechanical  Engineers;  Member  of  Cleveland  Institu- 
tion of  Engineers;  Chief  of  the  Technical  Department  of  Richardsons,  Westgarth 
and  Co.,  Ltd. 

Author  of  "The  Steam  Turbine." 

ROBERT  WILSON 

Author  of  "Treatise  on  Steam  Boilers,"  "Boiler  and  Factory  Chimneys,"  etc. 


CHARLES  PROTEUS  STEINMETZ 

Consulting  Engineer,  with  the  General  Electric  Co.;  Professor  of  Electrical  Engineering, 
Union  College. 

Author  of  "The  Theory  and  Calculation  of  Alternating-Current  Phenomena,"  "Theo- 
retical Elements  of  Electrical  Engineering,"  etc. 


JAMES  J.  LAWLER 

Author  of  "Modern  Plumbing,  Steam  and  Hot- Water  Heating." 

WILLIAM  F.  DURAND,  Ph.  D. 

Professor  of  Marine  Engineering,  Cornell  University. 

Author  of  "Resistance  and  Propulsion  of  Ships,"  "Practical  Marine  Engineering." 

HORATIO  A.  FOSTER 

Member,  American  Institute  of  Electrical  Engineers;  American  Society  of  Mechanical 

Engineers;  Consulting  Engineer. 
Author  of  "Electrical  Engineer's  Pocket-book." 

^- 

ROBERT  GRIMSHAW,  M.  E. 

Author  of  "Steam  Engine  Catechism,"  "Boiler  Catechism,"  "Locomotive  Catechism," 
"Engine  Runners'  Catechism,"  "Shop  Kinks,"  etc. 


SCHUYLER  S.  WHEELER,  D.  Sc. 

Electrical  Expert  of  the  Board  of  Electrical  Control,  New  York  City;  Member  American 

Societies  of  Civil  and  Mechanical  Engineers. 
Author  of  "Practical  Management  of  Dynamos  and  Motors." 


Authorities  Consulted— Continued 


J.  A.  EWING,  C.  B.,  LL.  D.,  F.  R.  S. 

Member,  Institute  of  Civil  Engineers;  formerly  Professor  of  Mechanism  and  Applied 
Mechanics  in  the  University  of  Cambridge;  Director  of  Naval  Education. 

Author  of  "The  Mechanical  Production  of  Cold,"  "The  Steam  Engine  and  Other  Heat 
Engines." 

^« 

LESTER  G.  FRENCH,  S.  B. 

Mechanical  Engineer. 
Author  of  "Steam  Turbines." 


ROLLA  C.  CARPENTER,  M.  S.,  C.  E.,  M.  M.  E. 

Professor  of  Experimental  Engineering,  Cornell  University;  Member  of  American 
Society  Heating  and  Ventilating  Engineers;  Member  American  Society  Mechanical 
Engineers. 

Author  of  "Heating  and  Ventilating  Buildings." 
V» 

J.  E    SIEBEL 

Director,  Zymotechnic  Institute,  Chicago. 
Author  of  "Compend  of  Mechanical  Refrigeration." 
<V« 

WILLIAM  KENT,  M.  E. 

Consulting  Engineer;  Member  of  American  Society  of  Mechanical  Engineers,  etc. 
Author  of  "Strength  of  Materials,"  "Mechanical  Engineer's  Pocket-book,"  etc. 

^ 

WILLIAM  M.  BARR 

Member  American  Society  of  Mechanical  Engineers. 

Author  of  "Boilers  and  Furnaces,"  "Pumping  Machinery,"  "Chimneys  of  Brick  and 
Metal,  "etc. 

^* 

WILLIAM  RIPPER 

Professor  of  Mechanical  Engineering  in  the  Sheffield  Technical  School:  Member  of  the 

Institute  of  Mechanical  Engineers. 
Author  of  "Machine  Drawing  and  Design,"  "Practical  Chemistry,"  "Steam,"  etc. 


J.  FISHER-HINNEN 

Late  Chief  of  the  Drawing  Department  at  the  Oerlikon  Works. 
Author  of  "Continuous  Current  Dynamos." 


SYLVANUS  P.  THOMPSON,  D.  Sc.,  B.  A.,  F.  R.  S.,  F.  R.  A.  S. 

Principal  and  Professor  of  Physics  in  the  City  and  Guilds  of  London  Technical  College. 
Author  of  "Electricity  and  Magnetism,"  "Dynamo-Electric  Machinery."  etc. 


ROBERT  H.  THURSTON,  C.  E.,  Ph.  B.,  A.  M.,  LL.  D. 

Director  of  Sibley  College,  Cornell  University. 

Author  of  "Manual  of  the  Steam  Engine."  "Manual  of  Steam  Boilers."  "History  of  the 
Steam  Engine,"  etc. 


Authorities  Consulted— Continued 


JOSEPH  G.  BRANCH,  B.  S.,  M.  E. 

Chief  of  the  Department  of  Inspection,  Boilers  and  Elevators  :  Member  of  the  Board  of 

Examining:  Engineers  for  the  City  of  St.  Louis. 
Author  of    "Stationary  Engineering,"   "Heat  and  Light  from  Municipal  and   Other 

Waste,"  etc. 

*• 

JOSHUA  ROSE,  M.  E. 

Author  of  "Mechanical  Drawing  Self  Taught,"  "Modern  Steam  Engineering,"  "Steam 
Boilers,"  "The  Slide  Valve,"  "Pattern  Maker's  Assistant."  "Complete  Machinist,  "etc. 


CHARLES  H.  INNES,  M.  A. 

Lecturer  on  Engineering  at  Rutherford  College. 

Author  of   "Air  Compressors  and  Blowing  Engines."  "Problems  in  Machine  Design," 
"Centrifugal  Pumps,  Turbines,  and  Water  Motors,"  etc. 

T?» 

GEORGE  C.  V.  HOLMES 

Whitworth  Scholar  ;  Secretary  of  the  Institute  of  Naval  Architects,  etc. 
Author  of  "The  Steam  Engine." 

^» 

FREDERIC  REMSEN  HUTTON,  E.  M.,  Ph.  D. 

Emeritus  Professor  of   Medical  Engineering   in  Columbia  University  ;    Past  Secretary 

and  President  of  American  Society  of  Mechanical  Engineers. 
Author  of  "The  Gas  Engine,"  "  Mechanical  Engineering  of  Power  Plants,"  etc. 

*>» 

MAURICE  A.  OUDIN,  M.  S. 

Member  of  American  Institute  of  Electrical  Engineers. 
Author  of  "  Standard  Polyphase  Apparatus  and  Systems." 


WILLIAM  JOHN  MACQUORN  RANKINE,  LL.  D.,  F.  R.  S.  S. 

Civil  Engineer  ;  Late  Regius  Professor  of  Civil  Engineering  in  University  of  Glasgow. 
Author  of  "Applied  Mechanics,"    "The  Steam  Engine,"  "  Civil  Engineering."  "Useful 
Rules  and  Tables,"  "Machinery  and  Mill  Work,"  "A  Mechanical  Textbook." 

'V 

DUGALD  C.  JACKSON,  C.  E. 

Head  of  Department  of  Electrical  Engineering,  Massachusetts  Institute  of  Technology; 

Member  of  American  Institute  of  Electrical  Engineers. 
Author  of    "A  Textbook  on  Electro-Magnetism  and  the  Construction  of  Dynamos," 

"Alternating  Currents  and  Alternating-Current  Machinery." 

^« 

A.  E.  SEATON 

Author  of  "A  Manual  of  Marine  Engineering." 


WILLIAM  C.  UNWIN,  F.  R.  S.,  M.  Inst.  C.  E. 

Professor  of  Civil  and  Mechanical  Engineering,   Central  Technical   College,   City  and 

Guilds  of  London  Institute,  etc. 
Author  of  "Machine  Design,"   "The  Development  and  Transmission  of  Power,"  etc. 


Foreword 


THE  rapid  advances  made  in  recent  years  in  all  lines  of 
engineering,  as  seen  in  the  evolution  of  improved  types 
of  machinery,  new  mechanical  processes  and  methods, 
and  even  new  materials  of  workmanship,  have  created  a  dis- 
tinct necessity  for  an  authoritative  work  of  general  reference 
embodying  the  accumulated  results  of  modern  experience  and 
the  latest  approved  practice.     The  Cyclopedia  of  Engineering 
is  designed  to  fill  this  acknowledged  need. 

C.  The  aim  of  the  publishers  has  been  to  create  a  work  which, 
while  adequate  to  meet  all  demands  of  the  technically  trained 
expert,  will  appeal  equally  to  the  self-taught  practical  man, 
who  may  have  been  denied  the  advantages  of  training  at  a  resi- 
dent technical  school.  The  Cyclopedia  not  only  covers  the 
fundamentals  that  underlie  all  engineering,  but  places  the 
reader  in  direct  contact  with  the  experience  of  teachers  fresh 
from  practical  work,  thus  putting  him  abreast  of  the  latest 
progress  and  furnishing  him  that  adjustment  to  advanced 
modern  needs  and  conditions  which  is  a  necessity  even  to  the 
technical  graduate. 

C.  The  Cyclopedia  of  Engineering  is  based  upon  the  method 
which  the  American  School  of  Correspondence  has  developed 
and  successfully  used  for  many  years  in  teaching  the  principles 
and  practice  of  Engineering  in  its  different  branches. 

C.  The  success  which  the  American  School  of  Correspondence 
has  attained  as  a  factor  in  the  machinery  of  modern  technical 
and  scientific  education  is  in  itself  the  best  possible  guarantee 


for  the  present  work.  Therefore,  while  these  volumes  are  a 
marked  innovation  in  technical  literature—representing,  as  they 
do,  the  best  ideas  and  methods  of  a  large  number  of  different 
authors,  each  an  acknowledged  authority  in  his  work — they  are 
by  no  means  an  experiment,  but  are,  in  fact,  based  on  what  has 
proved  itself  to  be  the  most  successful  method  yet  devised  for 
the  education  of  the  busy  man.  The  formula  of  the  higher 
mathematics  have  been  avoided  as  far  as  possible,  and  every 
care  exercised  to  elucidate  the  text  by  abundant  and  appropri- 
ate illustrations. 

C.  Numerous  examples  for  practice  are  inserted  at  intervals; 
these,  with  the  text  questions,  help  the  reader  to  fix  in  mind 
the  essential  points,  thus  combining  the  advantages  of  a  text- 
book with  those  of  a  reference  work. 

C.  The  Cyclopedia  has  been  compiled  with  the  idea  of  making 
it  a  work  thoroughly  technical  yet  easily  comprehended  by  the 
man  who  has  but  little  time  in  which  to  acquaint  himself  with 
the  fundamental  branches  of  practical  engineering.  If,  there- 
fore, it  should  benefit  any  of  the  large  number  of  workers  who 
need,  yet  lack,  technical  training,  the  publishers  will  feel  that 
its  mission  has  been  accomplished. 

C.  Grateful  acknowledgment  is  due  the  corps  of  authors  and 
collaborators— engineers  and  designers  of  wide  practical  expe- 
rience, and  teachers  of  well-recognized  ability— without  whose 
co-operation  this  work  would  have  been  impossible. 


Table   of  Contents 


VOLUME 


CONSTRUCTION  OF  BOILERS  .        .        .        .    By  W.  S.  Newell}       Page  *11 

Materials  of  Construction— Rivets— Flanging  Plates— Welded  Joints— Staying- 
Tubes— Furnace  Flues— Calking — Boiler  Design— Horse- Power — Grate  Area — 
Chimney  and  Forced  Draft— Heating  Surface— Water- Level— Strength  of  Boilers 
— Riveted  Joints 


TYPES  OF  BOILERS Page   69 

Boiler  Attachments— Stationary,  Marine,  and  Locomotive  Boilers— Flue,  Fire- 
Tube,  and  Water-Tube  Boilers — External  and  Internal  Firing — Haystack  and 
Wagon  Boilers — Cornish,  Lancashire,  and  Galloway  Boilers — Multitubular  Boilers 
(Horizontal,  Vertical) — Return-Tube  and  Through-Tube  Boilers — Fire-Box 
Boilers— Horizontal  Water-Tube  Boilers— Vertical  Water-Tube  Boilers  (Wickes, 
Cahall,  Stirling,  Milne)— Peculiar  Types  (Hazelton,  Harrison) 

BOILER  ACCESSORIES By  W.  S.  Leland       Page  143 

Boiler  Setting— Supports— Furnaces— Grates— Bridge— Smoke  Prevention— Down 
Draft— Hollow  Arch— Fuel  Economizers— Mechanical  Stokers— Fusible  Plugs- 
Natural  and  Forced  Draft — Steam,  Vacuum,  and  Water  Gauges — Try-Cocks — 
Gauge-Glasses  —  Valves  —  Check- Valves  —  Safety- Valves  —  Reducing  Valves- 
Evaporators— Feed-Water  Heaters— Steam  Separators— Steam  Traps— Calori- 
meters—Piping — Lagging — Horse-Power — Corrosion  and  Incrustation — Explo- 
sions— Fuel — Boiler  Trials 

STEAM  PUMPS By  A.  L.  Rice       Page  263 

Principles  of  Action— Lifting  and  Force  Pumps— Jet,  Rotary,  Centrifugal,  and 
Reciprocating  Pumps— Valves  'Flexible,  Hinged,  Poppet,  etc.)— Single,  Duplex, 
and  Triplex  Pumps — Condenser  Pumps — Air-Pumps — Steam  Valves — Compound 
Pumps— Testing 

REVIEW  QUESTIONS Page  363 

INDEX Page  371 


*  For  page  numbers,  see  foot  of  pages. 

t  For  professional  standing  of  authors,  see  list  of  Authors  and  Collaborators  at 
front  of  volume. 


Si 


Z  is 
11 


CONSTRUCTION  OF  BOILERS. 


A  steam  boiler,  or  steam  generator,  consists  of  a  vessel  to 
contain  the  water  and  the  steam  after  it  is  formed ;  a  fire-box  to 
contain  the  fire  ;  tubes,  flues  and  uptake  to  transmit  heat  and  con- 
duct the  hot  gases  from  the  fire  to  the  chimney,  and  various  fittings 
to  facilitate  the  safe  and  economical  operation.  Boilers  are  often 
classified  according  to  their  uses  and  conditions ;  thus  we  have 
stationary,  marine  and  locomotive  boilers.  Boilers  having  a  shell 
partially  filled  with  tubes,  through  which  the  hot  gases  pass,  are 
called  tubular,  fire- tube  or  shell  boilers;  and  those  having  a  large 
flue  in  which  is  placed  the  fire,  are  called  flue  boilers.  If  the  tubes 
are  filled  with  water  and  the  hot  gases  are  outside,  the  boiler  is 
called  a  water-tub'e  boiler. 

Steam  boilers  are  made  in  a  variety  of  shapes,  according  to 
the  type,  uses  and  conditions.  Let  us  first  consider  boiler  con- 
struction in  general,  leaving  out  the  peculiarities  of  marine,  loco- 
motive and  water-tube  boilers. 

MATERIALS. 

The  materials  of  which  boilers  are  constructed  are  exposed 
to  conditions  which  weaken  them  and  shorten  the  life  of  the  boiler. 
Among  these  conditions  are  corrosion,  both  external  and  internal, 
high  pressure,  and  expansion  and  contraction,  due  to  varying  tem- 
perature and  pressure. 

Cast  iron  was  the  material  of  which  the  earliest  forms  of 
boilers  were  made,  but  on  account  of  its  low  tensile  strength  audits 
unreliable  nature,  it  is  now  but  little  used,  except  for  parts  of  water- 
tube  boilers,  and  sometimes  for  the  ends  of  low-pressure  cylin- 
drical boilers  and  for  fittings.  It  is  cheap  and  resists  corrosion 
but  on  account  of  its  unreliability  and  brittleness,  the  parts  must 
be  made  thick  and  therefore  heavy. 


CONSTRUCTION    OF    BOILERS. 


Wrought  iron,  up  to  about  1870,  was  the  principal  material 
used  for  boiler  plates.  It  is  a  pure  iron  prepared  from  pig  iron 
by  a  process  called  puddling,  described  in  "  Metallurgy."  Wrought 
iron  is  well  adapted  for  use  in  boiler  construction,  as  it  is  strong, 
tough  and  fibrous,  and  combines  high  tensile  strength  with  ductil- 
ity and  freedom  from  brittleness.  When  the  properties  mentioned 
are  well  combined,  wrought  iron  will  resist  strains  due  to  unequal 
expansion.  Boiler  fastenings,  stays  and  other  parts  made  by 
welding  are  sometimes  made  of  wrought  iron.  It  is  customary  to 
consider  that  a  bar  loses  about  one-quarter  of  its  strength  by  weld- 
ing, although  it  is  often  stronger  in  the  weld,  owing  to  the  working 
of  the  metal  during  the  welding  process. 

Steel  has  entirely  displaced  iron  for  boiler-shell  work.  Boiler 
steel  is  made  by  the  open-hearth  process,  and  contains  for  ordinary 
thickness  of  1  or  1|  inches  0.25  per  cent  carbon,  while  thinner  plates 
of  |  inch  should  not  contain  over  0.15  per  cent  carbon.  Larger 
percentages  of  carbon,  while  accompanied  by  an  increase  in  tensile 
strength,  lessen  the  ductility.  The  following  properties  show 
steel  to  be  the  best  boiler  material  at  present :  great  tensile 
strength,  ductility,  homogeneity,  toughness,  freedom  from  blisters 
and  internal  unsoundness.  Blisters  and  unsoundness  are  faults 
sometimes  met  with  in  wrought-iron  plates. 

Copper  in  many  respects  is  superior  to  wrought  iron  for  boiler 
construction.  It  is  homogeneous,  resists  oxidation  (the  corrosive 
action  of  most  feed  waters)  and  incrustation.  It  is  more  ductile 
and  malleable  and  a  better  conductor  of  heat,  which  not  only  gives 
it  a  higher  evaporative  power,  but  also  enables  it  to  last  longer 
under  the  intense  heat  of  the  furnace.  Its  disadvantages  are  its 
low  tensile  strength,  about  30,000  pounds  per  square  inch,  and  its 
decrease  of  strength  with  an  increase  of  temperature.  In  heating 
from  the  freezing  point  to  the  boiling  point  it  loses  5  per  cent  of 
its  strength,  and  at  550°  F.  it  loses  about  one-quarter  of  its  strength. 
For  these  reasons  and  on  account  of  its  high  price,  it  is  now  seldom 
used  in  boiler  work. 

Brass  is  an  alloy  of  copper  and  zinc  in  which  the  proportions 
of  each  vary  considerably.  The  red  color  comes  from  a  larger  per 
cent  of  copper.  Red  brass  is  better  and  more  expensive  than  yel- 
low brass.  Brass  is  used  for  valves,  gauges  and  other  fittings. 


.CONSTRUCTION    OF    BOILERS. 


Bronze  is  an  alloy  of  copper  and  tin,  and  is  advantageously  used 
for  valves  and  seats  of  safety  valves  where  the  wear  is  great. 


TESTING   MATERIALS. 


In  order  to  determine  the  strength  and  the  other  qualities  of 
the  materials,  specimens  are  tested.  The  results  of  these  tests 
show  the  ultimate  tensile  strength,  elastic  limit,  contraction  of  area 
and  elongation. 


13 


CONSTRUCTION    OF    BOILERS. 


The  simplest  way  to  test  a  piece  of  iron  bar  or  plate  would 
be  to  fix  it  firmly  at  the  upper  end  and  hang  weights  on  the  other 
end,  adding  other  weights  until  the  bar  is  broken.  This  is  but  a 
crude  method,  and  in  order  that  the  elastic  limit  and  elongation 
may  be  determined  at  the  same  time,  testing  machines  are  used. 
There  is  a  large  variety  of  testing  machines,  adapted  for  various 
materials,  but  the  general  principles  are  the  same. 

Testing  Machines.  The  testing  machine  consists  of  a  frame 
and  two  heads,  to  which  the  ends  of  the  test  piece  are  fastened  by 
wedges  or  other  devices.  By  means  of  steam  or  hydraulic  power 
one  head  is  drawn  away  from  the  other  for  tensile  tests.  The  pull 
is  transmitted  to  some  weighing  device,  usually  levers  and  knife 
edges  like  the  beam  of  ordinary  platform  scales.  In  small  machines 
the  pull  may  be  applied  by  a  lever. 


E 

3 

vf 

^/           st 

o 

o 

J                    S^cvi 

T 

J>        T 

Fig.  2. 

Testing  machines  are  made  for  all  varieties  of  testing:  tensile, 
compressive  and  shearing  stresses.  Also  for  deflection  of  beams 
and  for  strength  of  wood,  cement,  brick  and  stone.  Fig.  1  shows 
an  Olsen  testing  machine  designed  for  tensile  and  compressive 
tests  of  iron  and  steel. 

In  order  to  test  materials,  test  pieces  or  specimens  are  pre- 
pared. For  testing  iron  plate  the  test  piece  should  be  at  least  1 
inch  wide,  about  2  feet  long  and  planed  on  both  edges.  Many 
engineers  recommend  these  dimensions.  According  to  the  Board 
of  Supervising  Inspectors  of  Steam  Vessels,  the  test  piece  should 
be  10  inches  long,  2  inches  wide  and  cut  out  at  the  center. 

To  ascertain  the  tensile  strength  and  other  qualities  of  steel, 
a  test  piece  should  be  taken  from  each  plate.  These  test  pieces 
are  made  in  the  form  as  shown  in  Fig.  2.  The  straight  part  in 


CONSTRUCTION    OF    BOILERS. 


the  center  is  9  inches  long  and  1  inch  wide  ;  and  to  determine 
elongation  it  is  marked  with  light  prickpunch  marks  at  distances 
1  inch  apart,  the  marked  space  being  8  inches  in  length.  The 
ends  are  1^  inches  to  2  inches  broad  and  3  inches  to  6  inches  long. 
As  has  been  explained  in  "  Mechanics,"  the  force  necessary  to 
break  the  piece  is  the  proportionate  part  of  the  tensile  strength 
per  square  in  h.  Thus  if  the  test  piece  having  a  reduced  section 
of  .4  square  i  ch  is  broken  at  19,200  pounds,  the  tensile  strength 

19  200 
of  the  plate  is  -  ! =  48,000  pounds  per  square  inch. 

EXAMPLES   FOR  PRACTICE. 

1.  If  a  piece  of  boiler  plate  breaks  at  33,500  pounds  and  the 
reduced  section  is  1|-  inches  by  ^  inch,  what  is  the  ultimate  ten- 
sile strength? 

Ans.  59,555  pounds. 

2.  A  boiler  plate  is  claimed  to  be  of  64,000  pounds  tensile 
strength.     If  the  section  is  1  inch  wide  and  .63  inch  thick,  what 
should  be  the  reading  of  the  testing  machine  when  the  specimen 
breaks  ? 

Ans.  40,320  pounds. 

3.  A  test  piece  of  the  form  shown  in  Fig.  2  measured  8 
inches  between   the  prickpunch  marks  before  testing   and  9.56 
inches  after  testing.     What  was' the  per  cent  of  elongation  ? 

Ans.  19-1  per  cent. 

4.  If  the  area  of  section  before  breaking  is  .4825  square  inch 
and  after  breaking  is  .236  square  inch,  what  is  the  per  cent  of 
reduced  area? 

Ans.  51  per  cent. 

STRENGTH  OF  BOILER  flATERIALS. 

The  crushing  strength  of  cast  iron  is  high,  varying  from 
50,000  to  75,000  pounds  per  square  inch ;  its  tensile  strength  is 
low,  varying  with  the  chemical  and  physical  properties  of  the  iron 
from  about  15,000  to  22,000  pounds  per  sqr.are  inch. 

Wrought-iron  plates  having  a  tensile  strength  of  from  50,000 
to  60,000  pounds,  with  an  elongation  or  ductility  of  from  20  per 
cent  to  30  per  cent,  are  suitable  for  boiler  work.  Boiler  iron  may  be 


CONSTRUCTION    OF    BOILERS. 


tested  in  the  following  ways  if  testing  machines  are  not  available : 
Cut  from  the  plate  a  strip  about  2  inches  wide  and  bend  it  cold, 
down  upon  itself ;  if  it  shows  no  fracture  on  the  outside  curve,  it  is 
satisfactory.  This  is,  however,  a  severe  test,  and  only  the  best 
flange  iron  will  stand  it ;  on  the  other  hand,  any  iron  which,  when 
heated  to  a  cherry  red  and  bent,  shows  cracks  or  fracture  on  the 
outer  curve,  is  unfit  for  use  in  boiler  construction.  When  wrought 
iron  was  used  for  boiler  plates  it  was  customary  to  give  the  plate 
what  is  called  the  hammer  test.  The  plate  was  suspended  clear 
of  the  ground  and  struck  with  a  hammer  at  intervals  of  three  or 
four  inches  over  its  surface ;  a  clear,  ringing  tone  indicating  a  sound 
plate,  while  a  dull  sound  indicated  with  fair  certainty  a  defect  such 
as  internal  unsoundness. 

Mild  steel  has  a  tensile  strength  of  from  55,000  to  65,000 
pounds  per  square  inch,  with  an  elongation  of  25  per  cent.  A  test 
piece  cut  from  a  plate  |  inch  thick  or  less  should  stand  bend- 
ing double,  when  hot  or  cold,  and  not  show  any  cracks  ;  thicker 
plates  should  be  capable  of  being  bent  at  a  small  radius  to  a  large 
angle  without  showing  any  cracks.  Steel  should  never  be  worked 
at  a  blue  heat,  as  in  this  state  it  is  very  brittle.  It  is  also  mechan- 
ically tested  by  being  heated  to  a  cherry  red,  quenched  in  water  at 
82°  F.  then  bent  in  a  curve  of  small  radius ;  if  it  cracks,  it  has 
become  tempered,  and  it  is  therefore  unsuitable  for  this  work.  If 
the  tensile  strength  of  the  steel  is  under  70,000  pounds  per 
square  inch,  it  is  sufficiently  tough  and  ductile  and  can  be  easily 
worked. 

In  general,  boiler  materials  are  carefully  tested  for  the 
following  qualities : 

Tensile  strength,  to  resist  rupturing  strains.  Also  in  order 
that  the  plates  may  be  thin. 

Toughness  and  elasticity,  to  resist  corrosion  ar.d  the  wear  and 
tear  of  manufacture. 

Ductility,  so  that  the  boiler  may  change  its  shape  slightly 
without  rupture.  This  is  a  more  important  quality. 

BOILER  CONSTRUCTION    IN    DETAIL. 

The  drawing  or  design  of  the  boiler  is  worked  out  in  the 
draughting  room,  as  explained  later  under  the  head  of  Boiler  Design* 


16 


CONSTRUCTION    OF    BOILERS. 


The  draught  shows  the  general  arrangement  of  the  boiler,  together 
with  complete  detail  drawings,  from  which  the  materials  are 
ordered.  These  materials  are  plates,  rods  for  stays,  rivets,  stay 
bolts,  tubes,  steel  bars,  angles  and  channel  bars  for  stiffening,  etc. 
In  some  boiler  shops  it  is  customary  to  lay  the  boiler  out  on 
a  large  blackboard  full  size,  thereby  checking  the  drawing.  In 
ordering  plates  the  blank  forms  are  filled  out  in  the  following 


Messrs.  John  Blank  $  Co : 

Please  furnish  us  with  the  following  Steel  Plates,  Ultimate 
Tensile  Strength,  60,000  ;  Elongation,  25  per  cent : 


Number 
wanted. 

Thickness 

Dimensions. 

Marks. 

Remarks. 

6 

1" 

9o"x70" 

S  14 

Shell 

The  dimension  which  runs  in  the  direction  the  plate  is  to  be 
bent  is  given  first.  The  plates  are  marked  as  per  order  blank,  and 
this  serves  to  identify  the  plate  when  the  occasion  arises.  When 
ordering  any  odd  shape,  a  sketch  with  dimensions  must  be  placed 
in  the  column  headed  "  Remarks." 

In  ordering  plates,  allow  for  trimming,  particularly  in  the  case 
of  irregular  shapes.  Rivets  are  sold  by  the  pound,  regardless  of 
their  shape  or  size.  Round  and  flat  iron  may  be  ordered  by  the 
running  foot.  Manufacturers  publish  tables  showing  weight  of 
rivets,  round  iron,  etc.,  with  which  they  furnish  boiler  makers. 

Boiler  shops  are  equipped  with  the  following  tools:  plate  rolls, 
plate  planers,  shears,  drill  presses,  punches,  countersinking  ma- 
chines, flanging  machines,  hydraulic  and  steam  riveters,  and  a 
compressed-air  system  for  operating  pneumatic  machines,  such  as 
calkers  and  chipners.  They  also  have  machine  shops  for  doing 


IT 


10  CONSTRUCTION    OF    BOILERS. 


such  machine  work  as  is  required  for  fittings,  furnace  fronts,  etc., 
and  a  system  of  cranes  for  handling  and  transporting  material. 
In  connection  with  the  above  is  a  storeroom  of  sufficient  size,  a 
forge  shop,  and  an  engine  and  boiler  for  supplying  the  shop  with 
the  power  necessary  to  operate  it. 

In  boiler-shell  work  drilling  has  entirely  displaced  punching, 
and  to-day  all  holes  are  drilled.  Punching  is  cheaper  than  drill- 
ing, but  it  is  more  injurious  to  the  plates  and  not  as  accurate.  It 
is  easy  to  see  that  drilling  rivet  holes,  even  if  twenty  are  being 
drilled  at  once,  is  done  with  less  strain  on  the  plates  than  when 
done  by  a  multiple  punch  forcing  several  holes  at  once.  The  force 
required  to  punch  a  plate  gives  the  best  idea  of  the  harm  done 
to  the  plate.  Experiment  shows  that  the  resistance  of  a  plate  to 
punching  is  about  the  same  as  its  resistance  to  tensile  tearing. 
Suppose  this  to  be  50,000  pounds  per  square  inch  ;  then  the  force 
required  to  punch  the  plate  is  the  area  cut  out  times  the  shearing 
strength,  or  d  X  TT  X  t  X  50,000. 

In  which  formula 

d  —  Jiameter  in  inches  and 
t  =  thickness  in  inches. 

For  a  hole  |  inch  in  diameter  in  a  ^--inch  plate,  the  force 
will  be 

|  X  3.1410  X  %  X  50,000  =  58,900  pounds. 

If  the  force  required  to  punch  one  hole  is  58,900  pounds,  the 
force  required  in  punching  several  holes  by  means  of  a  multiple 
punch  is  enormous. 

A  good,  ductile  plate  is  but  little  injured  by  punching ;  but 
if  of  a  hard,  steely  nature,  it  is  likely  to  be  seriously  injured.  For 
this  reason  wrought-iron  plates  are  usually  punched  and  steel 
plates  are  drilled.  On  the  whole,  a  drilled  plate  is  somewhat 
stronger  than  a  punched  plate  for  any  kind  of  joint. 

Some  boiler  makers  punch  the  rivet  holes  slightly  smaller 
than  the  desired  size  and  then  ream  them  out.  By  this  process 
the  injured  metal  around  the  holes  is  cut  away.  Another  method 
to  overcome  the  injurious  effects  is  to  anneal  the  plate  after 
punching. 

The  ordinary  process  of  annealing  consists  of  heating  the 
plate  to  red  heat,  and  then  allowing  it  to  cool  slowly.  By  this 


18 


-CONSTRUCTION  OF  BOILERS. 


11 


means,  hard  and  brittle  iron  or  steel  is  made  soft  and  tough. 
While  the  metal  is  hot,  the  surface  becomes  oxidized.  For  most 
purposes  this  scale  of  oxide  in  not  harmful,  but  in  some  cases  it 
must  be  removed.  As  this  is  expensive,  a  process  of  annealing 
in  illuminating  gas  has  been  devised.  The  action  of  the  gas  is  to 
reduce  the  oxide  without  altering  the  properties  of  the  piece.  The 
results  obtained  from  annealing  depend  upon  the  kind  of  iron  or 
steel,  the  temperature  to  which  it  is  raised,  and  the  rate  of  cool- 
ing. It  is  a  great  advantage  to  all  steel  of  over  64,000  pounds  per 
square  inch  in  tensile  strength,  but  softer  steels  are  little  better 
for  the  process. 


After  the  shell  plates  are  planed  to  correct  shape  and  the 
holes  drilled  or  punched,  they  are  put  through  the  bending  rolls 
and  bent  into  a  cylindrical  shape,  the  amount  of  curvature  being 
determined  by  a  template  made  for  the  purpose.  Plates  are 
usually  sheared  to  size,  and  then  the  edges  planed  with  a  slight 
bevel  to  facilitate  calking.  In  the  meantime  the  heads  are  being 
flanged  by  a  hydraulic  flanging  machine  ;  when  the  flange  is  com- 
pleted, the  head  is  put  on  the  platen  of  a  boring  mill 'and  turned  so 
as  to  exactly  fit  into  the  shell.  In  some  shops  it  is  customary  to 
punch  or  drill  only  a  few  holes  in  the  shell  and  flange  of  the  head, 
these  holes  serving  to  take  bolts  for  holding  the  parts  together. 
The  back  head  plate  is  bolted  into  the  rear  course  of  plating,  and 


I-J 


CONSTRUCTION    OF    BOILERS. 


the  parts  thus  assembled  are  hoisted  up  to  drill  if  the  plates,  etc., 
have  not  been  previously  drilled  or  punched,  otherwise  to  the 
hydraulic  riveter. 


RIVETS   AND   RIVETING. 

Rivets  are  formed  by  forging,  from  round  iron  bar  or  mild 
steel,  with  a  cup  or  pan  shaped  head.  The  cylindrical  part,  called 
the  shank,  is  a  little  smaller  than  the  hole  and  has  a  slight  taper. 
Fig.  3  shows  common  forms  of  rivets.  As  rivets  are  not  as  reli- 
able in  tension  as  in  shear,  they  are  used  mainly  at  right  angles  to 
the  straining  force.  If  the  stress  is  parallel  to  the  axis,  bolts  are 
used,  since  they  are  strong  in  tension.  The  shearing  strength  of 
steel  rivets  is  about  45,000  pounds  per  square  inch,  and  of  iron 
rivets  about  40,000  pounds  per  square  inch.  Steel  rivets  are  often 
used  with  steel  plates,  but  many  boiler  makers  prefer  to  use  iron 
rivets  in  all  cases. 

Three  types  of  rivets  in  use  are  shown  in  Fig.  4,  the  follow- 
ing table  giving  the  dimensions: 


Diameter 
of  Rivet. 

Cone  Head. 
A 

Countersunk. 
B 

Button  Head. 
C 

D 

E 

F 

a 

E 

Q 

E 

G 

I 

1A 

H 

T9* 

.1A 

& 

IA 

A 

B 

H 

H 

H 

IA 

5 

Te 

H 

^ 

1 

H 

H 

i* 

H 

1 

H 

A 

I 

IA 

H 

1 

H 

A 

IA 

i 

i 

y 

H 

M 

i  & 
x# 

ir 

if 

1 

Formerly  all  joints  of  boilers  were  riveted  by  hand,  but  now 
all  riveting  is  done  by  machines,  except  those  joints  to  which,  a 
machine  cannot  be  applied.  If  done  by  hand,  the  red-hot  rivet  is 
inserted  in  the  hole,  and  the  second  head  formed  by  two  riveters 
working  with  hammers.  This  head  is  either  made  conical  by  the 
hammers  alone  or  finished  with  a  cup-shaped  die  called  a  "snap." 
This  latter  is  the  more  usual  method.  The  disadvantages  of  hand 
riveting  are  slowness  and  a  tendency  to  form  a  shoulder  before  the 
rivet  fills  the  hole. 


CONSTRUCTION    OF    BOILERS. 


13 


Machine  riveting  is  preferable,  as  the  work  is  done  better, 
faster  and  more  accurately  ;  the  pressure  coming  gradually  on  the 
entire  rivet,  compresses  it  completely  into  the  hole  before  the  head 
is  formed.  Before  riveting,  care  should  be  taken  that  the  plates 
are  close  together,  so  that  a  shoulder  will  not  be  formed  between 
the  plates  and  prevent  a  good  joint.  Rivets  should  always  be  put 
in  while  red  hot,  for  in  this  condition  they  are  more  easily  worked, 
and  when  they  cool  they  contract,  nipping  the  plates  together  in  a 
tight  joint. 

Hydraulic  riveting  is  more  gradual  and  is  generally  preferred 
to  steam  riveting.  The  pressure  from  the  steam  riveter  often 
comes  as  a  sudden  blow  and  does  not  allow  time  for  the  rivet  to 
completely  fill  the  hole. 


D  — * 


<—  D 


B 

Fig.  4. 


It  is  sometimes  desirable  to  rivet  with  a  countersunk  head ; 
that  is,  the  rivet  does  not  project  above  the  plate.  The  counter- 
sunk head  is  formed  by  hammering  down  the  end  of  the  rivet  into 
the  countersink  in  the  plate.  This  form  is  shown  at  D,  Fig.  3. 
This  joint  is  often  used  in  shipbuilding  and  in  boiler  making  when 
it  is  necessary  to  attach  mountings.  It  should  always  be  avoided, 
if  possible,  on  account  of  its  weakness,  and  especially  when  the 
straining  force  acts  in  the  direction  of  the  length  of  the  rivet,  as 
the  head  has  a  very  insecure  hold  and  is  likely  to  be  pulled  through 
the  hole. 

Rivets  may  be  tested  in  a  boiler  shop  as  follows- :  the  rivet  to 
be  bent  cold  in  the  form  of  a  hook  around  another  rivet  of  the 


21 


14 


CONSTRUCTION    OF    BOILERS. 


same  diameter,  and  show  no  flaws  or  cracks ;  to  be  bent  hot 
down  upon  itself  and  show  no  cracks,  head  to  be  flattened  while 
hot  until  its  diameter  is  21  times  the  diameter  of  the  shank,  and 
show  no  flaws. 

The  uniform  heating  of 
steel  rivets  is  of  more  im- 
portance than  in  the  case  of 
iron  rivets,  where  it  is  suffi- 
cient to  heat  the  points  only. 
Steel  rivets  also  should  not 
be  heated  to  a  white  heat,  as 
iron  rivets  are,  but  to  a 
bright  cherry  red,  for  if 
heated  beyond  this  point  they 
will  burn.  The  fire  in  which 


Fisr.  5. 


steel  rivets  are  heated  should 
be  kept  thick,  and  the  draught 

moderate.     This  should  also  be  observed  in  heating  steel  plates 

for  flanging. 

There  are  various  forms  and  strengths  of  riveted  joints.     It 


Fig. 


is  obvious  that  in  punching  or  drilling,  a  plate  is  weakened  to  the 
extent  of  the  sectional  area  cut  out,  and  that  if  the  holes  are 
punched,  the  metal  between  the  holes  is  weakened.  In  treating 
the  strength  of  a  joint  it  is  customary  to  speak  of  it  'as  a  percent- 
age of  the  strength  of  an  unpunched  plate. 

If  one  plate  overlaps  another  and  is  riveted  to  it  by  a  single 


CONSTRUCTION    OP    BOILERS. 


row  of  rivets,  as  shown  in  Fig.  5,  it  is  called  a  single-riveted  lap 
joint.  This  joint  has  about  56  per  cent  of  the  strength  of  a  solid 
plate.  If  another  row  of  rivets  is  added,  it  is  called  a  double- 
riveted  lap  joint;  Fig.  6  shows  the  double-riveted  lap  joint  chain 
riveted,  and  Fig.  7  the  double-riveted  lap  joint  zigzag  riveted. 
Double  riveting  is  done  in  two  ways  :  zigzag,  or  staggered, 
and  chain.  When  rivets  are  put  in  so  that  the  rivets  of  one  row 
are  opposite  the  spaces  of  another  row,  it  is  called  zigzag  riveting 
or  staggered  riveting.  If  the  rivets  are  placed  immediately  oppo- 
site each  other,  it  is  called  chain  riveting. 


1C 


If  the  two  plates  are  kept  in  the  same  plane  and  a  cover  or 
butt  strap  riveted  on,  it  is  called  butt  riveting  (Fig.  8,  in  which  A 
and  B  are  the  boiler  plates,  and  C  is  the  butt  strap).  If  an  inside 
butt  strap  is  added,  it  is  called  a  double  butt  joint  (Fig.  9).  Fig. 
10  shows  a  treble-riveted  butt  joint.  A  single  butt  joint  is  about 
equal  in  strength  to  a  lap  joint  having  but  one  row  of  rivets,  but 
a  double  butt  joint  is  considerably  stronger. 

In  this  latter  form  of  joint  the  rivets  have  double  shearing 
surfaces,  since  they  tend  to  shear  off  in  two  planes.  This  either 
makes  a  stronger  joint  or  allows  the  use  of  smaller  rivets.  In  the 
single  butt  joint  the  butt  strap  is  usually  about  1^  the  thickness 
of  the  plate,  and  if  the  inside  butt  strap  is  added,  each  butt  strap 


16 


CONSTRUCTION    OF    BOILERS. 


*       *       * 


is  made  about  j  the  plate  thickness.     Butt  joints  are  now  being 

used  in  the  best  class  of  boilers,  and  are  used  almost  entirely  for 

plates  less  than  1  inch  in  thickness. 

Lap  joints  are  used 
for  circumferential 
seams,  and  the  stronger 
joint,  the  butt,  for  longi- 
tudinal joints.  For  high 
pressures  in  marine 
boilers,  triple  riveting 
is  frequently  used. 

If  a  cover  plate  is 
riveted  on  the  outside 
of  a  lap  joint,  it  is  called 
combined  lap  and  butt 
joint.  In  this  ease 

there  are  three  rows  of  rivets,  the  middle  row  having  twice  as 

many  rivets   as   the    outer  .rows.     Fig.   11   shows   the  combined 

joint. 

The  distance   between    the   centers  of   rivets  is   called    the 

"  pitch."     The  mathematical  calculation  of  pitch  and  the  distance 

between  the  rivets  and  the  edge  of  the  plate  will  be  taken  up 

later. 

The  following  table  gives  an  idea  of  the  relative  strengths 

of  riveted  joints : 


Kind  of  Joint. 

Riveting. 

Percentage  of  Strength. 

Punch. 

Drilled. 

Lap 

Single 
Double 

55 
69 

62 

75 

Single  Butt 

Single 
Double 

55 
69 

62 
•75 

Double  Butt 

Single 
Doubte 

57 

72 

67 
79 

24 


CONSTRUCTION    OF    BOILERS. 


17 


FLANGING  IRON  AND  STEEL  PLATES. 

Iron  plates  are  more  severely  tested  by  flanging  than  by  any 
other  work  done  upon  them.  This  is  due  to  their  fibrous  nature, 
and  great  care  is  necessary  to  prevent  breaking  in  the  bend,  if 
the  corner  is  sharp. 


Fig.  10. 


As  has  been  stated,  steel  requires  uniform  heating  and 
moderate  curves.  Flanging  is  almost  entirely  done  to-day  by 
machines.  After  flanging,  the  steel  should  be  annealed  by  heat- 
ing the  whole  plate  uniformly  to  a  dull  red  heat,  and  allowing  it 
to  cool  slowly. 

WELDED  JOINTS. 

Welded  joints  for  boiler  shells  are  desirable.  By  their  use 
deposits  which  accumulate  on  and  around  rivet  heads  and  joints, 
corrosion  caused  by  leakage,  and  loose  rivets,  are  done  away  with, 
and  calking  also.  Moreover,  a  perfectly  welded  joint  is  stronger 
than  the  best  riveted  joint,  and  approximates  nearly  to  the  origi- 
nal strength  of  the  plate.  Welded  steam  drums  are  used  now 
quite  extensively  for  water-tube  boilers  of  the  marine  type. 

The  soundness  of  such  a  joint  is  a  matter  of  uncertainty,  and 


25 


18 


CONSTRUCTION    OF    BOILERS. 


Fig.  11. 


depends  upon  the  skill  and  care  of  the  workmen.  It  is  impos- 
sible, from  external  appearances,  to  judge  the  soundness  of  a 
welded  joint.  The  principal  use  of  welded  joints  is  for  furnace 
tubes  and  steam  domes,  but  they  have  not  been  used  much  for 

boiler  shells.  The 
lack  of  tests  on 
welded  joints  and 
the  small  amount  of 
information  on  the 
subject,  render  the  re- 
sults of  experiments 
of  little  value.  The 
weld  is  best  made 
when  the  edges  of 
the  plates  are  upset, 
at  red  heat,  to  nearly 
double  the  plate  thickness,  and  beveled  to  an  angle  of  about  45 
degrees.  The  edges  are  then  heated  together,  and  the  weld  made 
by  hammering  down  the  joint  to  the  original  thickness  of  tV 
plate. 

ARRANGEHENTS  OF  PLATES   AND  JOINTS. 

When  we  take  up  the  design  of  boilers  we  shall  see  that  a 
boiler  tends  to  rupture  longitudinally.  The  reason  for  this  is 
that  the  resistance  of  a  thin  cylinder  to  circumferential  rupture  is 
double  the  resistance  to  longitudinal.  Since  this  is  the  case,  lap 
joints  are  used  for  transverse  seams,  and  a  stronger  form  (the 
double  butt  joint)  is  used  for  the  longitudinal. 

At  the  junction  of  three  or  more  plates,  where  the  circumfer- 
ential and  longitudinal  joints  meet,  ordinary  riveted  joints  would 
be  too  thick.  To  overcome  this  difficulty,  two  or  more  plates  are 
forged  thin  at  the  joint,  as  shown  in  Fig.  12. 

Whenever  longitudinal  and  girth  seams  meet,  the  plates 
should  be  arranged  to  "break  joints";  that  is,  one  longitudinal 
seam  should  not  be  a  continuation  of  another.  The  proper  ar- 
rangement is  shown  in  Fig.  13. 

In  both  vertical  and  horizontal  boilers  the  inside  lap  is  made 
to  face  downward,  so  that  it  will  not  form  a  ledge  for  the  collec- 
tion of  sediment 


26 


12 

g"ar 


CONSTRUCTION-    OF    BOILERS. 


19 


The  belts  of  plates  that  make  up  the  length  are  sometimes 
arranged  conically,  with  the  outside  lap  facing  backward.  When 
the  boiler  is  slightly  inclined 
toward  the  front  end,  this 
conical  arrangement  f  a  c  i  1  i  - 
tates  draining  and  cleaning, 
as  the  dirt  is  removed  at  the 
front  end.  This  is  a  great 
advantage  to  internally  fired 
boilers,  as  they  are  difficult 
to  clean. 

In  long  vertical  boilers 
the  ring  seams  are  arranged 
with  the  inside  lap  facing 
downward,  so  as  not  to  have 
a  ledge  for  sediment.  Some- 
times the  belts  of  locomotive 
boilers  are  arranged  telescopi- 
cally,  with  the  largest  diam- 
eter at  the  fire-box  end.  Of 
late  years  the  best  makers 
use  larger  plates  than  formerly.  This  is  advantageous,  espe- 


cially in  externally  fired  multitubular  boilers,  as  the  single  seam  is 
placed  above  the  water-level,  and  therefore  is  away  from  the  fire. 


CONSTRUCTION    OF    BOILERS. 


The  portion  of  a  boiler  between  the  shell  and  the  furnace  is 
called  the  water  leg.  Figs.  14  to  20  inclusive  illustrate  the 
method  of  construction  of  the  water  leg  and  the  joints  around  the 
furnace  door.  Figs.  14  and  15  show  two  methods  of  constructing 


14. 


o  o  o 

o  o  o 

o  o  o 

o  o  o 

o  o  o 

000 


o 

O  i 

o 
o 
o 
o 
o 
o 
o 
o 
o 

8- 

o 
o 


ooooooooa 


Fig.  15. 


the  water  leg.  In  Fig.  14  the  exterior  plate  and  the  furnace  plat3 
are  riveted  to  the  ring  D  by  means  of  long  rivets.  This  ring  is 
usually  made  of  wrought  iron,  but  in  many  cheap  boilers  it  is  of 
cast  iron.  In  Fig.  15  the  two  plates  are  riveted  to  the  flanged 
ring  D.  This  construction  is  better  than  the  solid  cast-iron  ring, 
on  account  of  flexibility,  but  the  junction  of  the  plates  D  and  C 


CONSTRUCTION    OF    BOILERS. 


21 


forms  a  corner  in  which  sediment  is  deposited.  In  Fig.  17  the 
plate  B  is  flanged  and  riveted  to  C.  This  arrangement  requires 
less  riveting  than  the  one  shown  in  Fig.  15.  Figs.  14,  15  and  IT 
also  show  three  forms  of  construction  o£  the  joints  around  the 


Fig.  16. 


Fig.  18. 


13  's 

T^ 

o 

0 

^^x 

wrfiftWi1 

)  O  C 
)  0  C 
)  0  C 
)  0  C 
)  0  C 
)  0  C 

(0000 

o 
o. 

A 

W//////A 

(  )l 

••--•  :••;: 

oooooc 

'//////Ms 

\-J  I 

0B 

O  i 

o 

v°^ 

\c 

\( 

oc| 

'///////M. 

1'il.l.hl.M.Mll 

S 

oa 

Fig.  17. 


furnace  door.  In  Fig.  14  both  the  exterior  plate  and  the  furnace 
sheet  are  flanged  and  riveted  together.  This  is  shown  in  an  en- 
larged view  in  Fig.  18.  The  construction  shown  in  Figs.  15  and 
19  is  not  as  good  as  that  in  Fig.  14,  because  of  the  extra  riveting ; 
also,  it  has  two  corners,  B  and  C,  for  the  deposit  of  sediment. 
Fig.  1 7  shows  a  somewhat  different  form  of  furnace  construction, 


29 


22 


CONSTRUCTION    OF    BOILERS. 


the  two  plates  being  riveted  to  the  cast-iron  ring.  This  form  it 
better  shown  in  Fig.  20.  It  makes  this  part  of  the  boiler  too 
rigid,  but  it  has  the  advantage  of  not  having  rivet  heads  to  wear 
off.  In  these  methods  of  riveting,  those  which  have  the  flanged 
ring  are  preferable  to  those  using  the  cast-iron  ring,  because  of 
more  freedom  for  expansion ;  but  the  flanged  ring  forms  an 
undesirable  corner. 


Fig.  19. 


Fig.  20. 


In  almost  every  boiler,  plates  must  be  connected  at  right 
angles.  An  example  of  this  is  seen  where  the  end  plates  art 
jointed  to  the  shell  plates  of  cylindrical  boilers.  There  are  three 
principal  methods :  riveting  both  plates  to  an  angle  iron,  riveting 
to  a  flanged  ring  and  flanging  the  end  plate.  In  Fig.  21  the  two 
plates  are  riveted  to  an  angle  iron,  which  is  made  of  wrought  or 
cast  iron.  This  construction  is  too  rigid  ;  the  constant  variations 
of  temperature  cause  repeated  changes  of  form,  which  tend  to  crack 
the  angle  iron  on  the  inside  of  the  plate  at  the  joint.  Corrosion 
increases  the  evil,  as  it  rapidly  attacks  iron  which  has  once  been 
cracked  or  broken.  There  is  no  definite  rule  for  the  dimensions 
of  these  angle  irons,  but  it  is  safe  to  make  the  mean  thickness  a 
little  greater  than  that  of  the  plates. 

The  forms  shown  in  Figs.  22  and  23  are  better.  The  head 
is  flanged  and  riveted  to  the  shell  plates.  The  flanging  makes  a 
more  flexible  joint.  The  radius  of  the  curve  of  the  flange  should 
be  about  four  times  the  thickness  of  the  plate.  The  head  and 


30 


CONSTRUCTION    OF    BOILERS. 


23 


shell    are   sometimes   connected   to  a  flanged    ring,  as  shown   in 
Fig.  24.     The  extra  row  of  rivets  makes  a  complex  joint. 

In  vertical  boilers  the  external  fire-box  is  joined  to  the  cylin- 
drical shell  by  riveted  joints.  Figs.  25  and  26  show  two  forms; 
that  in  Fig.  25  being  the  better  on  account  of  the  flanged  ring, 


Fig.  21. 


Fig.  22. 


Fig.  23. 


Fig.  24. 


which  allows  expansion  and  contraction  of  the  shell  and  furnace 
plates. 

Sometimes  the  case  occurs  of  connecting  two  plates  which  are 
parallel  and  near  together.     For  instance,  at  the   bottom  of  the 


Fig.  26. 


locomotive  fire-box  a  connection  must  be  made  between  the  inner 
and  outer  fire-box.  The  water-leg  construction  is  a  similar  case. 
Several  methods  for  this  construction  are  shown  in  Fig.  27. 
Fig.  27A  is  too  complicated  and  is  undesirable,  both  on  account 
of  the  numerous  rivets  and  angle  irons,  and  on  account  of  the  in- 
side joints,  which  cannot  be  calked.  Fig.  27 B  is  better,  since  it 
has  but  one  angle  iron ;  it  has,  however,  the  undesirable  inside  joint. 


24 


CONSTRUCTION    OF    BOILERS. 


Fig.  27o  is  a  good  joint,  the  form  of  connection  being  called  a 
channel  iron.  Fig.  27E,  as  we  have  seen,  is  a  good  flexible  joint, 
but  it  has  the  undesirable  corner  where  sediment  lodges. 

We  have  thus  briefly  discussed  the  various  methods  and 
arrangements  for  putting  shells  together,  and  now  let  us  return  to 
our  boiler,  which  is  ready  for  riveting  at  the  hydraulic  riveter.  A 
few  rivets  are  first  driven  at  equal  intervals  around  the  ring  seam 


A  B  C  D  E 

Fig.  27. 

at  the  back  head.  The  reason  for  driving  only  a  few  rivets  is 
that  any  errors  in  the  spacing  of  the  holes  are  distributed  and  not 
accumulated,  as  would  be  the  case  if  they  were  driven  in  succes- 
sion. From  this  point  on,  the  riveting  is  continued  until  the  shell 
is  completely  riveted  up. 

STAYING. 

The  shell  is  now  ready  to  receive  the  stays.  When  under 
steam,  a  cylindrical  shell  is  strained  by  internal  pressure  in  two 
directions,  namely :  transversely,  by  a  circumferential  strain  due  to 
the  pressure  tending  to  burst  the  shell  by  enlarging  its  circumfer- 
ence, and  longitudinally,  by  the  pressure  on  the  ends.  If  a  boiler 
were  spherical  it  would  require  no  stays,  because  a  sphere  sub- 
jected to  internal  pressure  tends  to  enlarge  but  not  to  change  its 
shape.  All  Hat  surfaces  in  boilers  must  be  stayed,  otherwise  the 
internal  pressure  would  bulge  them  out  and  tend  to  make  them 
spherical  in  shape.  The  ends  of  steam  drums  on  high-pressure 
water-tube  boilers  are  often  made  hemispherical. 

The  first  and  most  important  point  in  staying  is  to  have  a 


CONSTRUCTION    OF    BOILERS. 


25 


sufficient  number  of  stays  so  that  they  will  entirely  support  the 
plate  without  regard  to  its  own  stiffness.  The  second  is  to  have 
them  so  placed  as  to  present  the  least  obstruction  to  a  free  inspec- 
tion, and  third,  to  have  them  so  arranged  as  to  allow  a  free  circu- 
lation of  water.  Too  much  care,  cannot  be  taken  in  fitting  stays 
and  braces,  as  they  are  out  of  sight  for  long  periods,  and  a  knowl- 
edge of  their  exact  condi- 
tion is  not  always  easily 
obtained.  In  the  ordinary 
fire-tube  boiler  the  princi- 
pal surfaces  stayed  are: 
the  flat  ends,  crown  sheets, 
flat  sides  of  locomotive 
boilers  and  combustion 
chambers  of  cylindrical 
marine  boilers.  In  t  h  e 
case  of  most  marine  or 

Scotch  boilers,  the  diameter  is  large  compared  to  the  length  ;  hence 
the  flat  surface  is  considerable,  and  needs  careful  staying.  All 
the  plates  that  are  not  cylindrical  or  hemispherical  must  be 
stayed.  The  details  should- be  arranged  for  each  boiler;  a  few 
general  methods  and  cautions  can,  however,  be  given. 

The  most  common  and  simple  form  of  stay  is  a  plain  rod.    It 
is  used  to  stay  the  flat  ends  of  short  boilers.     This  stay  is  a  plain 


Fig.  29. 

rod  passing  .through  the  steam  space  and  having  the  ends  fastened 
to  the  heads.  The  ends  are  fastened  and  the  length  adjusted  in 
a  variety  of  methods ;  the  simplest  being  nuts  on  both  sides 
of  the  plate,  as  shown  in  Fig.  28.  The  copper  washers  a  and  b 
strengthen  the  plate  and  prevent  abrasion  by  the  nuts.  In  place 
of  the  nuts  the  rod  is  often  bolted  to  angle  irons,  which  are  riveted 
to  the  plates.  In  this  case,  turn  buckles  similar  to  the  one  shown 
in  Fig.  29  are  used  for  adjusting  the  length. 


33 


CONSTRUCTION    OF    BOILERS. 


The  stays  are  usually  from  |  inch  to  an  inch  in  diameter, 
and  are  made  of  wrought  iron  or  steel,  with  an  allowable  stress  of 
5,000  to  7,000  pounds  per  square  inch.  If  the  ends  are  fastened 
to  riveted  angle  irons,  the  combined  area  of  the  rivets  is  made  a 
little  greater  than  that  of  the  rod. 


Fig.  30. 

If  a  boiler  is  long,  that  is,  more  than  20  feet,  long  stays 
would  sag  in  the  middle  and  not  take  up  the  full  stress  on  the 
end  plates.  For  long  boilers,  gusset  and  diagonal  stays  are  used. 
This  form  of  boiler  stay,  shown  in  Fig.  30,  is  made  of  wrought- 


Fig.  31. 

iron  plate  riveted  to  angle  irons  ;  the  angle  irons  being  riveted  to 
the  end  and  shell.  Boilers  of  the  Cornish,  Lancashire  and  Gallo- 
way types  often  have  this  kind  of  stay.  These  boilers  are  inter- 
nally  fired,  and  as  the  variation  of  temperature  causes  expansion 
and  contraction,  great  care  should  be  used  in  placing  the  gusset 


.  .  CONSTRUCTION    OF    BOILERS. 


stay.     If  the  stay  is  too  near  the  flange  or  too  many  stays  are 
used,  the  head  will  be  too  rigid  and  have  a  tendency  to  crack. 

A  form  of  diagonal  stay  is  shown  in  Fig.  31.  The  plain  rod 
is  connected  to  angle  irons  by  means  of  split  phis.  The  angle 
irons  are  fastened  to  the  shell  and  end  by  rivets  or  bolts.  Another 
form  of  diagonal  stay,  called  the  crowfoot,  is  shown  in  Fig.  32. 
The  two  ends  are  bolted  or  riveted  to  the  end  and  shell. 


Fig.  32. 

The  angle  between  the  shell  plate  and  stay  rod  should  be 
small, —  not  more  than  30  degrees.  The  rod  itself  is  designed  foi' 
tensile  strength,  since  the  diagonal  pull  may  be  easily  reduced  to 
an  equivalent  direct  pull.  A  large  factor  of  safety  is  used  to 
provide  for  future  corrosion. 


Fig.  33. 

For  marine  boilers,  a  modified  crowfoot  stay  (Fig.  33)  is  often 
used.  The  end  passing  through  the  head  is  supplied  with  nuts 
and  taper  washers,  the  washers  having  the  proper  taper  to  allow 
the  nuts  to  be  set  up  tightly  against  them. 


35 


CONSTRUCTION"    OF    BOILERS. 


In  locomotive  fire-boxes  and  in  the  combustion  chamber  of 
marine  boilers,  there  are  two  flat  or  slightly  curved  surfaces  that 
must  be  stayed  together.  These  are  riveted  by  short  screw  stay 
belts.  The  bolts  shown  in  Figs.  34  and  35  are  screwed  in  place, 
and  the  ends  riveted  over.  In  marine  boilers  these  stays  are 
fastened  with  nuts,  as  shown  in  Fig.  36,  instead  of  being  riveted. 


Fig.  34. 


Fig.  35. 


Sometimes  the  bolt  is  threaded  the  entire  length,  as  in  Fig.  34,  or 
is  turned  off  smooth  in  the  center,  as  in  Fig.  35.  The  smooth  sur- 
face resists  corrosion,  and  is  less  likely  to  fracture  than  the  threaded 
bolt.  Sometimes  a  small  hole  is  drilled  in  the  end,  so  that  if  the 
bolt  breaks,  the  escaping  steam  will  give  warning.  This  is  shown 
at  a,  Fig.  34.  These  bolts  are  J  inch  or  1  inch  in  diameter. 

The  strains  which 
come  on  a  stay  bolt  are 
not  the  same  as  those 
on  rivets  or  on  ordinary 
stay  rods ;  as  a  matter 
of  fact,  stay  bolts  fail 
by  a  bending  stress,  and 
generally  fracture  just 
inside  the  outside  sheet, 
due  to  the  unequal  ex- 
pansion between  combustion  chamber  or  furnace  and  the  outside 
boiler  shell.  Owing  to  this  difference  of  expansion,  flexible  stay 
bolts  have  been  designed,  but  have  not  come  into  general  use,  nor 
are  they  likely  to,  as  they  occupy  considerable  space  and  are  much 
more  complicated  than  the  simple  stay  bolt.  Stay  bolts  are  made 
from  the  best  quality  of  refined  iron,  which  has  been  found  to 
stand  the  strains  of  alternate  heating  and  cooling  better  than 
mild  steel.  Iron  stay  bolts  are  more  durable,  because  of  the 
fibrous  nature. 


36. 


36 


CONSTRUCTION    OF    BOILERS. 


29 


It  should  be  added  that  boiler  heads  are  further  stiffened  by 
channel  bars  or  angles  placed  along  the  line  of  holes  for  the 
through  stay  rods. 


Fig.  37. 

The  crown  sheets  of  fire-boxes  and  tops  of  combustion 
chambers  are  usually  stayed  by  crown  bars,  which  extend  across 
the  flat  surfaces,  as  shown  in  Fig.  37,  the  ends  resting  on  the 


88. 


side  plates.  Bolts  about  4  inches  apart  connect  the  crown  sheet 
to  this  girder.  The  girder  may  be  a  solid  bar,  or  it  may  be  made 
up  of  two  flat  plates  bolted  or  riveted  together,  as  shown  in  the 
figure,  the  stay  bolts  being  placed  between  the  plates  at  intervals 


CONSTRUCTION    OF    BOILERS. 


of  about  4  inches.  Either  bolts  or  rivets  may  be  used  to  keep 
the  plates  which  form  the  girder  from  spreading.  Projections 
are  sometimes  forged  on  the  bottom  of  the  girder,  so  that  the  stay 
bqlts  may  be  screwed  up  tightly  without  bending  the  plate. 

The  depth  of  the  plates  which  make  up  the  girder  vary  from 


4  to  6  inches.  They  are  from  j  to  |  inch  in  thickness.  If  bolts 
|  inch  in  diameter  are  used,  the  distance  between  the  plates  is 
usually  1  inch,  but  if  larger  bolts  1  inch  in  diameter  are  used, 
the  distance  should  be  1J  inches.  The  ends  of  the  bars  which 
rest  upon  the  side  plates  should  be  carefully  fitted  to  make  a  good 
bearing,  and  the  area  should  be  sufficient  to  prevent  crushing  of 


Fig.  40. 

the  end  plates.  The  distance  between  the  crown  sheet  and  the 
girder  should  be  at  leasf,  1|  inches,  so  that  there  will  be  good 
circulation  and  the  plates  may  be  readily  cleaned. 

In  some  cases  the  girder  is  supported  from  the  shell  by  sling 
stays,  as  shown  in  Fig.  38.     The  sling  stays  are  connected  to  the 


35 


CONSTRUCTION    OF    BOILERS.  31 

girder  and  to  an  angle  iron,  or  T-iron,  which  is  riveted  to  the  shell. 
The  angle  iron  stiffens  the  shell.  In  designing  this  form  of  stay 
it  is  usual  to  make  the  girder  strong  enough  to  support  the  crown 
sheet  without  any  sling  stays,  and  these  stays  are  used  for  addi- 
tional support. 

TUBES. 

Boiler  tubes  are  made  of  steel  or  wrought  iron,  but  most 
commonly  of  charcoal  iron  and  lap  welded.  In  the  formation  of 
the  lap  the  plate  is  upset,  then  bent  around  until  the  thickened 
edges  lap  sufficiently.  It  is  then  heated  successively  about  8 
inches  at  a  time,  and  welded  over  a  mandrel,  which  is  a  cast-iron 


Fig.  41. 

arm  with  a  slightly  convex  top,  over  which  the  tube  is  placed 
Tubes  are  measured  by  their  outside  diameters,  and  are  usually 
true  to  gauge,  so  that  holes  for  them  may  be  bored  without  taking 
measurements  from  the  tubes  themselves. 

The  holes  for  the  tubes  in  the  tube  sheet  are  usually  made 
in  one  of  two  ways.  One  method  is  to  punch  the  tube  holes  the 
proper  size  by  means  of  a  helical  punch.  With  this  punch  the 
metal  is  cut  away  by  a  shearing  cut.  The  holes  ought  to  be 
punched  a  little  under  size,  and  then  reamed  out,  so  that  the  sur- 
face against  which  the  tubes  are  expanded  may  be  good.  The 
other  method  is  to  punch  or  drill  a  small  hole  at  the  point  mark- 
ing the  center  of  the  tube  hole.  A  drill  with  a  post  in  the  center, 
which  fits  the  small  hole,  then  drills  the  desired  size  of  hole. 


32  CONSTRUCTION    OF    BOILERS. 

Ordinary  tubes  are  fastened  to  the  end  plates  by  expanding 
the  metal  of  the  tube  against  the  tube  plate.  This  is  done  by  a 
tool  called  an  expander,  of  which  there  are  two  common  forms. 
One  form  consists  of  a  steel  taper  pin  and  a  number  of  steel  seg- 
ments, held  in  place  by  a  spring.  The  outside  of  the  segments 


Fig.  42. 

have  the  form  to  be  given  to  the  expanded  tube,  and  the  inside  is 
a  straight  hollow  cone,  into  which  the  steel  taper  pin  fits.  The 
segments  are  forced  apart  by  hammering  on  the  steel  pin.  In 
order  that  the  metal  of  the  tube  may  not  be  injured,  the  hammer- 
ing should  be  done  gradually  and  carefully,  and  the  expander 
turned  frequently.  Another  form,  shown  in  Fig.  39,  has  a  set  of 
rolls  that  are  forced  against  the  inside  of  the  tube  by  driving  in 
the  taper  pin.  The  pin  and  rolls  rotate  as  the  pin  is  driven,  and 

the  rolls  gradually  expand  the 
tube  against  the  tube  plate. 

Two  forms  of  tube  expan- 
sion are  shown  in  Figs.  40  and 
41.  That  shown  in  Fig.  41  is 
preferable  to  that  in  Fig.  40,  as 
the  latter  bears  at  the  corners 
only,  while  the  former  bears 
Fio.  4.,  against  the  entire  thickness  of 

the  tube  sheet. 

After  the  tubes  are  expanded,  the  ends  are  beaded  over,  as 
shown  in  Figs.  40  and  41.  This  adds  to  the  strength  of  the  con- 
nection between  the  tube  and  tube  sheet.  The  tool  commonly 
used  for  this  beading  is  shown  in  Fig.  42. 

Ferrules  are  often  placed  in  the  ends  of  fire  tubes,  and  serve 
to  protect  the  ends  from  the  intense  heat  of  the  fire.  The  ar- 
rangement is  shown  in  Fig.  43,  the  ferrule  F  being  placed  within 
the  tube  for  a  short  distance.  The  space  A  is  merely  an  air 
space. 


40 


CONSTRUCTION    OF    BOILERS. 


33 


Stay  tubes  are  not  used  as  extensively  at  the  present  time  aa 
they  were  formerly.  They  were  very  common  at  a  time  when  the 
holding  power  of  expanded  tubes  had  been  experimented  on  but 
little.  It  is  now  apparent  from  such  tests  that  the  holding  power 
of  tubes  expanded,  as  shown  in  Fig.  40,  is  more  than  equal  to  the 
pressure  on  the  spaces  between  the  tubes  of  an  ordinary  tube 
plate.  Stay  tubes  are  simply  heavier  tubes,  with  the  ends  pro- 


Fig.  44. 

jecting  beyond  the  tube  sheet  and  threaded  for  shallow  nuts. 
The  ends  of  the  tubes  are  frequently  upset  or  thickened,  and 
screwed  into  the  tube  sheet  as  well.  This  form  is  shown  in 
Fig.  44. 

FURNACE   FLUES. 

Flues  which  are  subjected  to  external  pressure    should  al- 
ways be  cylindrical.     Fig.  45  shows  the  section  of  the  Adamson 


Fig.  45. 


Fig.  46. 


flue.  This  was  an  improvement  over  the  plain  furnace,  as  it 
is  more  elastic  and  allows  expansion;  the  flanged  rings  also 
strengthen  and  stiffen  it  against  collapse.  The  methods  of  build- 
ing furnaces  shown  in  Figs.  46  and  47  are  not  considered  as  good 
as  the  Adamson  arrangement.  Fig.  46  is  too  rigid,  and  does  not 


41 


34 


CONSTRUCTION    OF    BOILERS. 


allow  a  free  expansion  and  contraction.  Fig.  47,  on  the  other 
hand,  permits  of  such  extremely  well,  but  both  have  the  fault  of 
exposing  a  double  thickness  of  plates  and  two  rows  of  rivets  to 
the  fire. 

The  corrugated  flue  shown  in  Fig.  48  is  popular  and,  fur- 
thermore, is  excellent.  There  is  freedom  for  expansion  through- 
out its  whole  length,  thereby  reducing  the  strains  on  the  boiler. 


Fig.  47. 

The  plates  should  be  thick  enough  to  prevent  sagging  in  the  mid- 
dle, the  thickness  usually  varying  from  -f^  inch  to  f  inch.  Cor- 
rugated furnaces  are  riveted  to  the  rear  tube  sheet  in  the  return 
tube  boiler  of  the  marine  type,  the  end  of  the  furnace  being 


Fig.  48. 

flanged  at  the  front ;  and  the  head  of  the  boiler  is  flanged  around 
the  opening  cut  for  the  furnace,  which  fits  well  into  the  flange. 


CALKING. 


In  order  that  riveted  joints  of  boilers  may  be  steam  and 
water  tight,  they  generally  require  calking.  This  process  up- 
sets the  metal  of  the  overlapping  plater  or  burrs  down  the  edge, 


THE  WICKES  VERTICAL  WATER  TUBE  BOILER. 


CONSTRUCTION    OF    BOILERS.  25 

forcing  it  into  close  contact  with  the  lower  plate,  and  rendering 
the  joint  steam  tight. 

The  calking  tool  is  similar  to  a  chisel,  the  end  having  a  va- 
riety of  shapes.  Fig.  49  shows  a  round-nosed  tool  which  burrs 
down  the  upper  plate  without  cutting  the  under  plate ;  but  it  is 
hard  to  start,  and  in  calking  with  such  a  tool  the  edge  is  first 
started  with  a  sharper  round-nosed  tool,  and  then  finished  with 
one  as  indicated  in  the  figure.  If  a  square-end  tool  is  used,  as 
shown  in  Fig.  50,  the  under  plate  is  likely  to  be  cut,  and  the 
plates  between  the  edge  and  the  rivet  be  separated.  The  most 
common  form  of  calking  tool  is  one  similar  to  the  one  shown  in 


.  \ I 

Fig.  49.  Fig.  60. 

Fig.  49,  except  that  the  end  is  flat,  with  a   slight  bevel,  and   not 
round. 

A  slight  bevel  given  the  plates  makes  both  calking  and  ful- 
lering more  easily  done.  When  the  calking  tool  is  thin  it  is 
sometimes  driven  by  careless  workmen  into  the  joint,  wedging  the 
plates  open.  Severe  and  careless  calking  is  very  injurious  to 
boilers.  On  the  inside  it  often  causes  grooving  and  fracture,  and 
the  fracture  of  plates  then  follows  the  line  of  calking  rather  than 
the  line  of  rivet  holes.  A  pneumatic  calking  machine  is  often 
used  in  boiler  shops,  as  it  does  this  work  about  four  times  as 
rapidly  as  it  can  be  done  by  hand.  It  resembles  a  rock  drill  in 
general  principles.  Air  is  supplied  through  a  flexible  tube,  at  a 
pressure  of  about  70  pounds  per  square  inch.  It  makes  about 
1,500  strokes  a  minute. 


143 


S6  CONSTRUCTION   OF   BOILERS 

BOILER    DESIGN. 

The  rules  of  boiler  design  are  controlled  by  practical  consid- 
erations and  theory,  and  are  learned  by  the  designer  by  practice 
only.  The  rules  vary  from  place  to  place,  and  from  time  to  time, 
due  to  progress  in  engineering. 

The  rules,  methods  and  cautions  taken  up  here  are  general,  and 
with  necessary  modifications  can  be  applied  to  all  the  more  com- 
mon types. 

In  designing  a  steam  boiler  there  are  several  considerations 
that  must  be  kept  in  mind.  Among  the  most  important  are 
strength,  durability,  capacity  to  furnish  the  required  amount  of 
steam,  convenience  for  cleaning,  repairing  and  inspection,  sim- 
plicity in  detail,  and  economy  both  of  running  and  first  cost. 

The  kind,  or  type,  to  be  used  depends  upon  the  work  to  be 
done,  the  diyness  of  the  steam,  the  locality,  the  available  space 
and  preference  of  the  owner.  The  work  to  be  done  is  determined 
by  the  number  and  kind  of  engines,  the  constancy  with  which 
they  run  and  the  pressure.  In  choosing  a  boiler  for  any  locality, 
the  purity  of  the  water,  the  kind  of  fuel  and  the  laws  which 
govern  inspection  and  allowable  working  stress  must  be  consid- 
ered. The  available  space  greatly  influences  the  type  and  some- 
times prevents  choice.  For  instance,  locomotive  and  marine  boil- 
ers must  be  put  in  a  small  space.  For  land  boilers  if  the  floor 
area  is  limited,  but  there  is  ample  height,  some  type  of  vertical 
boiler  must  be  chosen. 

HORSE    POWER. 

The  unit  of  horse-power  as  decided  by  the  American  Society 
of  Mechanical  Engineers  is  equal  to  83,305  B.  T.  U.  From  the 
standard  steam  tables  in  treatises  on  Thermo-dynamics  we  find 
that  966  B.  T.  U.  are  required  to  evaporate  one  pound  of  water  from 
and  at  212°  F.  Therefore  1  H.  P.  is  equal  to  the  evaporation  of 
33,305-^966  =  341  pounds  of  water  from  and  at  212°  F.  This  is 
•ilso  equal  to  the  evaporation  of  30  pounds  of  water,  at  100°  F. 
into  steam  at  70  pounds  gauge  pressure. 

The  first  thing  to  do  is  to  chose  the  type  of  boiler  we  are  to 
use.  Then  we  find  how  many  pounds  of  steam  are  to  be  supplied  per 
hour;  this  is  found  by  multiplying  the  desired  horse-power  by 


44 


'CONSTRUCTION  OF   BOILERS.  37 


34 },  or  multiplying  the  horse-power  of  the  engine  or  engines  by 
the  steam  consumption  per  horse-power  per  hour.  This  is  known 
approximately  for  every  type  of  engine. 

GENERAL    REQUIREflENTS. 

When  we  know  these  facts  we  design  our  boiler  so  as  to 
have : 

1.  Sufficient  area  of  grate  to  burn  the  required  amount  of 
fuel  under  the  given  draft. 

2.  Enough  heating  surface  to  absorb  the  heat  of  combustion. 

3.  Combustion  chamber  and  flue  area  large  enough  to  com- 
pletely burn  and  carry  off  the  products  of  combustion. 

4.  Water  space  sufficiently  large  so  that  a  sudden  demand 
will  not  cause  too  great  a  variation  in  water  level. 

5.  Surface  of  water  large  compared  to  volume,  in  order  that 
steam  may  be  rapidly  disengaged. 

6.  Steam  space  large  enough  to  supply  an  irregular  demand 
without  causing  a  great  change  of  pressure. 

7.  Steam  outlet  large  enough  to  supply  steam  to  the  engine 
without  wire-drawing. 

If  the  outlet  is  not  sufficiently  large  to  supply  plenty  of 
steam,  the  demand  will  be  greater  than  the  supply  and  the  steam 
will  be  throttled  or  wire-drawn,  that  is,  it  will  lose  some  pressure. 

For  all  common  types  of  boilers,  the  proportions  between  the 
above  requisites  have  been  determined  by  experiment  and  mathe- 
matics. These  relations,  with  simple  calculations  and  good  judg- 
ment on  the  part  of  the  designer,  are  all  that  are  needed  for  this 
work. 

AREA  OF  GRATE. 

A  square  foot  of  grate  area  will  burn  different  weights  of 
fuel  in  a  given  time,  according  to  the  nature  of  the  draft.  If  the 
boiler  can  be  made  of  any  size,  as  is  the  case  with  many  land 
boilers,  a  slow  rate  of  combustion  with  natural  draft  is  used,  as 
it  is  the  most  economical.  The  length  of  the  grate  is  limited  by 
the  distance  to  which  a  fireman  can  throw  coal  accurately. 
Usually  6  or  7  feet  is  the  limit.  In  locomotive,  torpedo  boat  and 
in  some  vertical  land  boilers,  the  size  of  grate  is  limited ;  in  order 

51909 

45 


CONSTRUCTION   OP  BOILERS. 


to  get  the  necessary  work  from  the  boiler,  forced  draft  is  used  and 
the  rate  of  combustion  increases  to  over  100  pounds  per  square 
foot  per  hour.  In  Lancashire  boilers,  with  two  internal  flues,  the 
breadth  is  limited.  The  rate  of  combustion  is  stated  in  pounds 
per  square  foot  of  grate  area  per  hour,  and  varies  with  the  type 
of  boiler  and  the  draft.  The  following  table  gives  the  rates  of 
combustion. 

CHIMNEY   DRAFT. 

Cornish  boilers,  slow  rate  4 — G    Ibs.  per  sq.  ft.  per  hour. 

Cornish  boilers,  ordinary  rate  10 — 15  Ibs.  per  sq.  ft.  per  hour. 

Factory  boilers,  ordinary  rate  12 — 18  Ibs.  per  sq.  ft.  per  hour. 

Anthracite  coal,  quick  rate  15 — 20  Ibs.  per  sq.  ft.  per  hour. 

Bituminous  coal,  quick  rate  20 — 30  Ibs.  per  sq.  ft.  per  hour. 

Marine  boilers,  ordinary  rate,  15 — 25  Ibs.  per  sq.  ft.  per  hour. 

Water  tube  boilers  10 — 25  Ibs.  per  sq.  ft.  per  hour. 

FORCED  DRAFT. 

Marine  boilers,  60 — 130  Ibs.    per  sq.  ft.  per  hour. 

Locomotive  boilers,  40 — 120  Ibs.    per  sq.  ft.  per  hour. 

The  evaporation  per  square  foot  of  grate  surface  depends 
upon  the  type,  the  rate  of  combustion,  condition  of  boiler  and  care 
in  firing.  The  highest  rate  is  obtained  with  slow  rate  of  combus- 
tion, care  and  skill  in  firing,  and  clean  plates  and  tubes.  The 
table  gives  the  equivalent  evaporation  per  pound  of  coal  for 
several  types. 

Plain  cylindrical  5 —  8  pounds. 

Vertical  7 — 10  pounds. 

Cornish  6 — 11  pounds. 

Lancashire  6 1-1 2  pounds. 

Galloway  9 — 12|  pounds. 

Multi  tubular  8 — 12  pounds. 

Water  tube  6—12  pounds. 

Marine  return  tube  7 — 12  pounds. 

Locomotive  6 — 12  pounds. 

Experiment  shows  that  an  increase  in  the  amount  of  coal 
burned  per  square  foot  of  grate  per  hour  gives  an  increase  in  the 


"CONSTRUCTION  OF   BOILERS.  39 

amount  of  water  evaporated  ;  but  a  decrease  in  amount  evaporated 
per  pound  of  fuel,  or  a  decrease  in  economy. 

To  find  the  area  of  grate  for  a  boiler.  Let  G  =  area  of 
grate  in  square  feet,  R  =  rate  of  combustion  in  pounds  per  square 
foot  per  hour,  E  =  evaporation  per  pound  of  coal. 


rp,        p     _ 


_  Pounds  of  water  evaporated 


E  X 


Let  us  take  an  example.  Suppose  we  have  an  externally 
fired  multitubular  boiler;  assume  the  rate  of  combustion  to  be  12 
pounds,  and  that  our  type  of  boiler  will  evaporate  9  pounds  of 
water  per  pound  of  coal.  How  large  must  the  grate  be,  if  2400 
pounds  of  water  are  evaporated  per  hour? 


Then  22.2  square  feet  of  grate  surface  are  necessary.  In  this 
case  the  grate  probably  would  be  made  6  feet  by  4  feet  or  24 
square  feet. 

TUBES. 

On  account  of  the  small  number  of  successful  experiments 
concerning  flues  and  chimneys,  it  is  usual  to  proportion  tubes,  flues 
and  chimneys,  by  comparison  with  those  that  have  given  good 
results.  If  the  tubes  are  too  large  the  hot  gases  in  the  centre  pass 
up  the  chimney  at  high  temperature.  Now  we  will  find  the  num- 
ber of  tubes.  Let  A  =•  total  area  in  square  feet  through 
which  the  smoke  passes,  that  is,  the  combined  internal  area  of  all 
the  tubes.  The  total  area  of  the  tubes,  A,  is  usually  made  ^  to  | 
the  area  of  the  grate.  If  we  design  our  boiler  to  have  the  ratio 
1:8  we  probably  will  have  enough  area.  Let  us  assume  our 
tubes  to  be  3  inches  in  diameter  and  16  feet  long.  From  the 
table,  on  page  40,  of  lap  welded  boiler  tubes  we  find  that  the  inter- 
nal area  of  a  3  inch  tube  is  6.08  square  inches,  the  internal  .  cir- 
cumference is  8.74  inches,  external  circumference  is  9.42  inches, 
and  the  external  area  is  7.07  square  inches.  As  |  of  our  grate 
surface  is  ^4-  or  3  square  feet,  or  432  square  inches,  the  number  of 
tubes  will  be  432  -f-  6.08  =  71. 


47 


40 


CONSTRUCTION  OF  BOILERS 


LAP  WELDED  BOILER  TUBES. 


External 
Diameter. 
Inches. 

Internal 
Diameter. 
Inches. 

Thickness. 
Inches. 

internal 
Circumference.  ; 
Inches. 

External 
Circumference. 
Inches. 

Internal  Area. 
Square 
Inches. 

External  Area. 
Square 
Inches. 

Length  of  tube 
persq.  ft.  inside. 
Feet. 

Length  of  tube 
per  sq.  ft.  outside. 
Feet. 

Weight 
per  foot. 
Lbs. 

1 

.856 

.072 

2.689 

3.142 

.575 

.785 

4.460 

3.819 

.708 

IX 

1.106 

.072 

3.474 

3.927 

.960 

1.227 

3.455 

3.056 

.900 

1% 

1.334 

.083 

4.191 

4.712 

1.396 

1.767 

2.863 

2.547 

1.25 

IK 

1.560 

.095 

4.901 

5.498 

1.911 

2.405 

2.448 

2.183 

1.665 

2 

1.804 

.098 

5.667 

6.283 

2.556 

3.142 

2.118 

1.909 

1.981 

2X 

2.054 

.098 

6.484 

7.069 

3.314 

3.976 

1.850 

1.698 

2.238 

2>^ 

2.283 

.109 

7.172 

7.854 

4.0!)4 

4  909 

1.673 

1.528 

2.755 

2K 

2.533 

.109 

7.957 

8.639 

5.039 

5.940 

1.508 

1.390 

3.045 

3 

2.783 

.109 

8.743 

9.425 

6.083 

7.069 

1.373 

1.273 

3.333 

3X 

3.012 

.119 

9.462 

10.210 

7.125 

8.296 

1.268 

1.175 

3.958 

3>^ 

3.262 

.119 

10.248 

10.995 

8.357 

9.621 

1.171 

1.091 

4.272 

3& 

3.512 

.119 

11.033 

11.781 

9.687 

11.045 

1.088 

1.018 

4.590 

4 

3.741 

.130 

11.753 

12.566 

10.992 

12.566 

1.023 

.955 

5.32 

W 

4.241 

.130 

13.323 

14.137 

14.126 

15.904 

.901 

.849 

6.01 

5 

4.720 

.140 

14.818 

15.708 

17.497 

19.635 

.809 

.764 

7.226 

6 

5.699 

.151 

17.904 

18.849 

25.509 

28.274 

.670 

.637 

9.346 

8 

7.636 

.182 

23.989 

25.132 

45.795 

50.265 

.500 

.478 

15.109 

10 

9.573 

.214 

30.074 

31.416 

71.975 

78.540 

.399 

.382 

22.190 

12 

11.542 

..229 

36.260 

37.699 

103.749 

113.097 

.330 

.318 

28.516 

16 

15.458 

.271 

48.562 

50.265 

187.667 

201.062 

.247 

.238 

45.200 

20 

19.360 

.320 

60.821 

62.832 

294.373 

314.159 

.197 

.190 

66.765 

48 


CONSTRUCTION  OF   BOILERS.  41 


STEAfl  SPACE. 

The  steam  space  is  frequently  designed  as  some  fraction 
of  the  volume  of  the  shell,  usually  about  i.  A  better  way  is  to 
design  it  from  the  steam  consumption  of  the  engine.  Suppose  the 
engine  uses  30  pounds  of  steam  at  75  pounds  pressure  per  H.  P. 
per  hour.  The  absolute  pressure  then  is  90  pounds  (nearly)  and 
the  specific  volume  at  that  pressure  is  4.85  (from  steam  tables). 
As  steam  is  being  generated  at  an  approximately  constant  rate,  the 
supply  kept  on  hand  need  hot  be  great.  If  the  surface  for  the 
disengagement  of  steam  is  sufficient,  the  ratio  of  the  steam  space  to 
the  volume  of  the  cylinder  is  from  50  :  1  to  150  :  1  depending  upon 
the  speed  of  the  engine.  Experiment  shows  that  if  the  steam 
space  is  equal  to  the  volume  of  steam  consumed  by  the  engine  in. 
20  seconds,  it  is  sufficient.  If  the  space  is  only  equal  to  the  steam 
used  in  12  seconds,  there  may  be  a  considerable  quantity  of  water 
carried  over  with  the  steam.  If  the  engine  is  slow  speed,  that  is 
less  than  60  revolutions  per  minute,  the  steam  space  should  be 
larger. 

The  volume  of  the  steam  space  per  H.  P.  will  be  the  number  of 
pounds  of  steam  used  per  H.  P.  in  20  seconds,  multiplied  by  its 

30  X  4.85  X  20 
specific  volume,  or  _  —  -  -  -   -    —   .81  cubic  feet    (nearly) 

per  H.  P.  ;  and  if  the  engine  is  of  75  H.  P.  our  steam  space  will 
be  .81  X  75  =  60.75  cvbic  feet. 

TUBE  SPACE. 

The  space  occupied  by  the  tubes  is  equal  to  their  volumes. 
The  volume  of  one  tube  is  its  external  area  multiplied  by  the 
length  in  inches.  The  total  volume,  in  cubic  inches,  is  the  above 
result  multiplied  by  the  number  of  tubes.  This  is  reduced  to 
cubic  feet  by  dividing  by  1728.  The  space  occupied  by  the  tubes 
will  be 

71  X  7.07X16X12  =  55.77  cubic  feet. 


WATER  SPACE. 

Then  if  we  assume  our  steam  space  to  be  £  the  volume  of  the 


49 


42  CONSTRUCTION"  OF   BOILERS. 

available  space  in  the  shell,  the  water  space  will  be  twice  the 
steam  space,  or  2  X  60.75  =  121.5  cubic  feet. 

DinENSIONS  OF  BOILER. 

The  volume  of  the  boiler  will  be  : 

Steam  space  .81  X  75  =  60.75  cubic  feet. 

rr  ,  71  X  7.07  X  16  X  12          .  -  _7      ,.    . 

Tube  space  — — -£l —  ;     55. 1 7  cubic  feet. 

Water  space  .81'X  75  X  2  =  121.5    cubic  feet. 

Total  space  ~1>MM~ cubic  feet. 

Since  the  tubes  are  16  feet  long  the  area  of  the  end  will  be 

238.02          .  Qf.,  ,    . 
.  =:  14. 8 1  square  feet. 

This  area  gives  a  diameter  of  about  4-i  feet  or  52  inches.  We 
will  make  the  boiler  4|  feet  or  54  inches  in  diameter.  Then 
the  boiler  will  be  16  feet  long  and  54  inches  in  diameter;  with 
7 1  tubes  3  inches  in  diameter.  For  moderate  power,  a  common 
rule  is  to  make  the  length  about  3|-  times  the  diameter ;  by  this 
rule  our  boiler  is  3.55  times  the  diameter. 

HEATING   SURFACE. 

The  portion  of  a  boiler  that  is  exposed  to  the  flames  and  hot 
gases  is  called  the  heating  surface.  This  is  made  up  of  the  por- 
tions of  the  shell  below  the  brickwork,  the  exposed  ends,  and  the 
internal  surface  of  the  tubes.  If  the  boiler  is  of  the  water  tube 
type,  the  exterior  surface  of  the  tubes  is  taken  in  place  of  the 
interior  surface. 

If  our  boiler  is  an  ordinary  multitubular  boiler  we  can  as- 
sume the  heating  surface  to  be  the  total  inside  area  of  the  tubes 
plus  one-half  the  area  of  the  shell.  Then: 

Heating  surface  of  tubes    8>74  X  ^  X  16  =  827.38  square  feet. 

Heating  surface  of  shell  14'137  *  16  _  113  1Q  gquare  f eet 

940.48  square  feet. 
The  ratio  of  heating  surface  to  grate  surface  will  be 

=  39.2  or  about  39. 


50 


'    CONSTRUCTION  OF  BOILERS.  43 

As  this  ratio  is  high  enough  we  will  not  alter  our  figures.  If  the 
ratio  had  been  too  low  we  could  have  added  more  tubes  and  found 
a  new  boiler  diameter.  The  heating  surface  should  not  be  less 
than  1  square  yard  or  9  square  feet  per  horse-power.  So 
940.48  -7-  75  =  12.54  or  our  boiler  has  12.54  square  feet  of  heating 
surface  per  horse-power.  This  is  of  course  abundantly  sufficient. 
The  capacity  of  heating  surface  to  transmit  heat  to  water 
depends  upon  conductivity,  position  of  surface  and  temperature 
of  furnace.  In  designing  it  is  safe  to  follow  proportions  of  heat- 
ing surface  to  grate  area  in  the  various  types,  which  experience 
has  shown  to  give  the  best  results.  The  following  are  the  pro- 
portions for  a  few  types. 


Marine,  Return  tube,  25  —  38 

Lancashire    boiler,  26  —  33 

Cornish,  27—32 

Horizontal,  internally  fired,  40  —  50 

Water  tube,  34  —  65 

Locomotive  boiler  (forced  draft),  80  —  34 

Marine,  28—32 

RATIO  OF  GRATE  SURFACE  TO  HORSE=POWER. 

The  ratio  of  grate  surface  to  horse-power  varies  with  the 
type,  as  is  shown  below. 

Kind  of  Boiler.  Ratio. 

Plain  cylindrical,  ,5     to  .7 

Multitubular,  .4     to  .6 

Vertical,  .6     to  .7 

Water  tube,  .3 

Lancashire,  .1     to  .165 

Marine  return  tube,  .12 

Locomotives,  .02  to  .06 

Makers  of  boilers  sometimes  estimate  the  H.  P.  by  the  heat- 
ing surface.  That  is  the  horse-power  is  a  fraction  of  the  heating 
surface.  The  ratio  of  heating  surface  to  H.  P.  for  several  types 
is  as  follows: 

f 

51 


44  CONSTRUCTION  OF   BOILERS. 

Plain  cylindrical,  6      — 10 

Multitubular,  14       —18 

Vertical,  15      —20 

Water  tube,  10      —12 

Marine  return  tube,  3.25 —  4 

Lancashire,  2.75 —  4.25 

Locomotive,  1      —  2 

It  is  evident  that  some  portions  of  the  heating  surface  of  a 
boiler  have  greater  efficiencies  than  others.  For  instance,  more 
heat  will  pass  through  the  crown  sheet  as  it  is  nearer  the  fire  than 
through  the  last  few  feet  of  the  tubes.  Taking  the  efficiency  of 
the  crown  sheet  as  1,  an  estimate  of  the  percentage  of  the  other 
parts  of  a  boiler  is  as  follows  : 

Crown  of  furnace  in  flue,  .95 

Plates  of  cylindrical  boiler  over  furnace,  .90 

Fire  box  tube  plate  of  locomotive  boiler,  .80 

Water  tube  surface  facing  fire,  .70 

Vertical  side  of  fire  box,  .50 

If  a  cylindrical  multitubular  boiler  is  divided  into  equal  sec- 
tions, the  section  nearest  the  fire  will  evaporate  more  water  than 
the  one  at  the  other  end,  as  the  gases  have  a  higher  temperature 
at  the.  first  section.  Suppose  we  divide  the  boiler  into  six  sec- 
tions of  equal  length,  and  call  the  total  evaporation  100  per  cent. 
Then  the  per  cent  of  evaporation  per  section  will  be  approximately 
as  follows  : 

Section  1       2       3       45       6 

Evaporation       47     23     14       8       5       3 

If  the  length  of  a  boiler  is  increased  another  section,  the 
evaporation  will  be  increased  a  little  but  at  the  same  time  the  radi- 
ating surface  is  increased.  In  case  the  addition  of  a  section  for 
evaporation  causes  a  loss  by  radiation  nearly  equal  to  the  gain  in 
evaporation,  it  is  not  economical  to  add  the  section  on  account  of 
the  extra  cost  of  the  boiler.  If  forced  draft  or  an  increase  of  air 
of  dilution  is  used,  the  boiler  should  be  made  longer  to  avoid  waste. 
The  air  of  dilution  is  the  amount  of  air  above  that  which  is  neces- 
sary to  burn  the  coal. 


52 


CONSTRUCTION  OF  BOILERS.  45 


WATER   LEVEL. 

If  the  steam  space  in  a  multitubular  boiler  is  known  the 
water  level  can  be  found,  for  the  section  of  the  steam  space  is  a 
segment  of  a  circle.  In  the  above  boiler  the  required  steam  space 
is  60.75  cubic  feet;  hence  the  segmental  area  is  60.75-^-16  or 
3.8  square  feet,  or  547.2  square  inches.  The  height  of  this  seg- 
ment is  15.55  inches.  This  height  is  found  either  by  calculation 
or  from  a  table  of  segments.  Then  the  mean  water  level  is  15.55 
inches  from  the  top  portion  of  the  shell.  The  variation  of  water 
level  in  a  boiler  of  this  type  and  size  should  not  exceed  6  inches. 

END   PLATE. 

The  end  plate  or  tube  sheet  is  usually  made  ^  or  |  inch 
thicker  than  the  shell  plates.  This  is  done  for  additional  stiffness, 
and  increase  of  strength  ;  the  plate  being  weakened  by  drilling 
the  holes  for  the  ends  of  the  tubes. 

The  tubes  should  be  arranged  in  vertical  and  horizontal  rows, 
if  possible,  in  order  that  the  rising  bubbles  of  steam  may  not  be 
hindered.  To  get  good  circulation  the  horizontal  spaces  should 
be  a  little  greater  than  the  vertical,  and  a  central  circulating 
space  should  be  provided,  if  the  necessary  number  of  tubes  can  be 
put  in  without  using  the  entire  space.  The  tubes  should  be  from 
|  to  1  inch  apart,  arid  to  prevent  burning  of  the  tubes,  the 
top  row  at  least  3  inches  below  the  water  level,  and  the  bottom 
tubes  6  inches  from  the  shell.  At  this  point,  a  drawing  of  the 
end  plate  should  be  made,  to  show  the  arrangement  of  tubes,  etc. 
If  it  is  impossible  to  put  in  the  required  number  of  tubes,  without 
raising  the  water  level,  the  diameter  of  the  boiler  must  be  in- 
creased. If  we  wish  to  increase  the  heating  surface  without  in- 
creasing the  diameter  we  can  use  smaller  tubes  or  make  the  boiler 
a  little  longer. 

STRENGTH  OF   BOILERS. 

According  to  Pascal's  Law,  liquids  and  gases  exert  pressure 
equally  in  all  directions.  Steam  in  a  boiler  exerts  the  same  pres- 
sure on  all  portions  of  the  shell.  As  the  pressure  inside  a  boiler 
is  considerably  greater  than  that  outside  (the  atmospheric  pres- 


46  CONSTRUCTION  OF    BOILERS. 

sure),  there  is  a  tendency  to  burst  the  shell.     This  tendency  is 
resisted  by  the  plates  of  the  boiler. 

A  sphere  is  the  strongest  form  to  resist  pressure,  for  since 
pressure  is  equal  in  all  directions,  there  is  a  tendency  towards  en- 
larging the  sphere  and  not  to  rupture.  But  a  sphere  has  the 
smallest  area  for  a  given  volume  and,  as  a  large  heating  surface  is 
desirable,  and  on  account  of  mechanical  difficulties,  a  spherical 
boiler  is  never  used.  The  boiler  is  made  cylindrical  to  obtain 
greater  heating  surface  and  the  loss  in  strength  is  made  up  by 
staying. 

In  the  consideration  of  the  strengtli  of  cylinders  it  is  usual  to 
divide  the  rupturing  strains  into  two  classes ;  those  which  tend  to 
rupture  the  cylinder  longitudinally  and  those  which  tend  to  rupt- 
ure it  circumferentially  or  transversely. 

Let  us  examine  them  separately.  The  tendency  tc  cause 
longitudinal  rupture  or  to  rend  the  cylinder  in  lines  parallel  with 
the  axis,  may  be  considered  as  the  pressure  exerted  on  a  semi- 
circumference,  and  tending  to  rupture  the  cylinder  in  a  plane 
through  the  diameter.  Since  pressure  acts  equally  in  all  direc- 
tions, the  whole  amount  exerted  on  a  semi-circumference  is  not 
exerted  directly  upwards  and  downwards.  But  all  these  forces 
may  be  resolved  into  their  vertical  and  horizontal  components. 
If  we  take  the  plane  as  horizontal,  it  is  evident  that  the  horizontal 
components  have  no  tensional  effect  at  the  points  of  rupture.  By 
taking  the  vertical  components  at  an  infinite  number  of  points  it 
can  be  proved  that  their  sum  is  equal  to  the  full  pressure  exerted 
on  a  rectangular  plane  equal  to  the  projection  of  the  cylindrical 
surface.  In  this  case  the  projection  is  the  plane  through  the 
diameter  and  has  an  area  equal  to  the  product  of  the  length  of 
the  cylinder  multiplied  by  the  diameter  of  the  cylinder.  Then 
the  force  tending  to  rupture  would  be  the  pressure  per  square 
inch  multiplied  by  the  area.  Let  p  =  pressure  in  pounds  per 
square  inch,  I)  =  diameter  of  boiler,  t  =  thickness  of  plate,  L  = 
length  of  boiler,  S  =  tensile  strength,  E  ^r  efficiency  of  joint, 
and  f  =  factor  of  safety.  .  The  force  tending  to  rupture  longi- 
tudinally will  be,  pLD.  The  strength  of  the  cylinder  to  resist 
this  rupturing  force  is  represented  by  the  tensile  strength  of  the 
material  multiplied  by  the  areas  of  sections  of  metal.  Or  expressed 


54 


,   CONSTRUCTION  OF  BOILERS. 


algebraically  is  2tLS.     When  rupture  is  about  to  take  place  the 
rupturing  force  and  the  strength  are  equal,  or 

pDL  =  2tLS    or    pD  =  2tS 

from  which  p  —   -  and  t  =  —    which  are    the    formulas  for 

pressure  and  thickness  and  for  longitudinal  strength. 

The  extra  pressure  due  to  increased  length  is  balanced  by  the 
increase  of  metal  as  is  shown  by  the  elimination  of  the  factor  L  of 
the  equation. 

The  tendency  to  rupture  circumferentially  is  evidently  repre- 

sented by  the  area  of  the  end  or  __      -    multiplied  by  the  pressure 

per  square  inch.     The  strength  to  resist  this  force  is  the  area  of 
metal  to  be  ruptured  multiplied  by  the  tensile  strength  or  TT  DtS 

7T  D2  -riiC 

—  X  p  =  TT  DtS 
4 

Dp  =  4tS 

By  comparing  these  two  formulas  we  see  that  with  the  same 
internal  pressure,  diameter  and  thickness  of  shell,  a  cylindrical 
boiler  is  twice  as  strong  transversely  as  it  is  longitudinally, 
hence  the  greatest  tendency  to  rupture  is  along  the  longitudinal 
seams. 

Therefore,  in  designing  the  thickness  of  shell  we  use  the 
formula  for  longitudinal  rupture, 

pD  =  2tS  or  t  =  ?P 
or,  inserting  the  factors  for  efficiency  of  joint  and  factor  of  safety, 


For  allowable  pressure    p  —    __ 
For  thickness  of  shell 


Now  let  us  find  the  thickness  of  the  boiler  that  we  are  design- 
ing. Suppose  after  testing  our  material  we  find  that  its  ultimate 
tensile  strength  is  54,000  pounds  per  square  inch.  In  this  case 
6  will  be  sufficiently  large  for  a  factor  of  safety.  This  factor  can 


43  CONSTRUCTION"  OF'  BOILERS. 

be  reduced  if  the  efficiency  of  the  joint  is  large.  Let  us  assume 
that  our  joint  has  an  efficiency  of  70  °/0.  This  is  merely  a  supposi- 
tion because  we  have  not  yet  constructed  the  joint ;  but  we  assume 
a  factor  in  order  to  find  a  trial  thickness. 

Then  t  =  BJ  =      °  X  54  X  75       =  .32  or  about  A  inches. 
2SE       2  X  54000  X  .7 

RIVETED  JOINTS. 

The  best  knowledge  of  the  strength  and  proportions  of 
riveted  joints  can  be  obtained  by  tests  of  full  sized  pieces.  Let  us 
consider  the  strength  and  efficiency  mathematically.  Riveted 
joints  may  fail  in  several  ways.  1.  By  shearing  the  rivets. 
2.  By  tearing  the  plate  at  the  reduced  section  between  the 
rivets.  3.  By  Crushing  the  plate  or  rivets  where  they  are  in 
contact.  4.  By  cracking  the  plate  between  the  rivet  hole  and 
the  edge  of  the  plate.  As  the  lap  in  practice  can  always  be  made 
sufficiently  wide  a  joint  need  never  fail  in  this  last  way. 

As  all  stresses  may  be  resolved  into  the  three  kinds,  tensile, 
compressive  and  shearing,  we  will  investigate  for  these  stresses. 
Let  P  =;  the  tensile  stress  transmitted  from  one  plate  to  the  other 
by  a  single  rivet,  t  =  the  thickness  of  the  plate,  d  =.  the  diameter 
of  the  rivet,  p  =  the  pitch,  and  St,  Ss  and  Sc  the  unit  stresses  in 
tension,  shear  and  compression  respectively  produced  by  P  on  the 
plates  and  rivets.  Therefore  the  tension  on  the  plate,  P  will  be 
equal  to  the  area  of  the  metal  between  the  rivets  multiplied  by  its 
unit  tensile  stress,  or 

P  r=  t  (p  —  d)  St 

For  shear,  P  will  equal  the  area  of  the  rivet  multiplied  by 
che  unit  shearing  stress,  or 

P    =i7Td2Ss 

For  compression,  the  stress  is  supposed  to  be  equivalent  to  a 
stress  uniformly  distributed  over  the  projection  of  the  cylindrical 
surface  on  a  plane  through  the  axis  of  the  rivet.  Then  P  will  be 
equal  to  the  area  of  the  projection  multiplied  by  the  unit  compres- 
sive  stress,  or 

F  =  tdSn 


56 


CONSTRUCTION  OF  BOILERS.  49 


The  above  formulas  are  for  single  riveted  lap  joints.  If  an- 
other row  of  rivets  is  used  the  plates  should  have  a  wider  lap.  Let 
p  =  the  pitch  in  one  row;  then  the  stress  will  be  distributed  over 
two  rivets. 

The  three  formulas  in  this  case  will  be. 
P  =  t(p  —  d)St 


For  single  riveted  butt  joint,  the  shear  comes  on  two  rivets; 
this  is  called  double  shear.  The  above  formulas  become 

P  =  t(p-d)St 
P  =  2  X  i77-d2S8 
P  =  tdSc 

The  efficiency  of  a  joint  is  the  ratio  of  its  allowable  stress  to 
the  allowable  stress  of  the  uncut  plate.  The  allowable  stress  of 
the  plate  is  represented  by  the  formula  ptSt. 

t  (  p  __  d  )  St       p  —  d 
Then  the  efficiency  for  tension  is,  E  =  —        ^   —  —  -  - 


tdSc        dSc         dSca 
1  or  compression,  E  =  --  or  or  - 


In  the  above  "formulas,  a  =  the  number  of  rivets  in  the  width 
p,  and  c  =  the  number  of  rivet  sections  in  the  same  space.  The 
smallest  value  of  E  is  to  be  taken  as  the  efficiency  of  the  joint 

In  designing,  we  try  to  get  a  joint  in  which  all  parts  will  have 
equal  strength  or  the  resistance  of  the  plate  to  tension  will  equal 
the  resistance  of  the  rivets  to  shearing  and  each  will  equal  the 
resistance  of  the  rivet  to  compression  or  crushing.  This  will  be 
the  case  if  the  three  efficiencies  are  equal. 

Solving  for  d  in  the  second  and  third  we  get 
^  TT  d2S8c       dSca  4aSct 

°       ~ 


ptSt        ~  pSt 
If  we  know  t  we  can  find  d  from  the  above  equation. 


67 


50  CONSTRUCTION  OF   BOILERS. 

To  find  the  pitch  we  make  the  first  equation  equal  to  the 
third,  or  the  formula  for  tension  equal  that  of  compression,  and 
solve  for  p 


substituting  the  value  for  d,  obtained  above, 


To  get  the  formula  for  efficiency  we  insert  these  values  for  d 
and  p,  in  any  of  the  formulas  for  efficiency  already  obtained.  For 
instance  : 

4aSct  (  S^a  +  1     _  4  aSct 

,    _   p  -  d  __  7T    CS8          St  TT    CS, 

- 


E  = 


A  good  joint  can  be  designed  without  these  formulas  (in 
fact  they  serve  as  a  guide  only),  if  attention  is  paid  to  the 
rules  deduced  from  tests  and  conforming  to  good  practice  by 
experienced  engineers  and  boiler  makers.  In  designing  a  riveted 
joint,  good  practice  favors  the  following : 

The  pitch  of  rivets,  for  single  riveting,  should  be  about  2| 
times  the  diameter  of  the.  rivets  and  for  double  riveting  about  3| 
times  the  diameter. 

The  pitch  near  a  calked  edge  must  not  be  too  great  for 
proper  calking. 

Rivets  must  not  be  too  near  together. 

The  lap,  or  the  distance  from  the  centre  of  the  rivet  to  the 
edge  of  the  over-lapping  plate  should  be  at  least  1|  times  the 
diameter  of  the  rivet. 

The  diameter  of  the  rivet  is  usually  nearly  twice  the  thick- 
ness of  the  plate  and  should  never  be  less  than  the  thickness  of 
the  plate. 

The  riveted  seam  must  contain  a  whole  number  of  rivets. 
and  similar  seams  should  have  the  same  pitch. 


58 


CONSTRUCTION  OP  BOILERS. 


51 


'The  distance  between  rows,  for  double  riveting,  is  about 
twice  the  diameter  of  the  rivets. 

In  double  butt  riveting  the  rivets  in  double  shear  have  1| 
times  the  single  section  instead  of  2 . 

The  thickness  of  double  butt  straps  should  not  be  less  than 
|  the  thickness  of  the  plate  (each)  ;  single  butt  straps  not  less 
than  |. 

No  one  set  of  rules  can  be  laid  down  for  the  best  pitch  of 
rivets  for  all  circumstances  of  pressure,  quality  of  plates,  etc. 
The  following  table  of  proportions  of  riveted  joints  gives  results 
for  average  practice  in  boilers  of  up  to  about  150  pounds 
pressure. 

TABLE  OF  LAP  JOINTS. 


Pitch.    Inches. 

Efficiency. 

Thickness 
of  Plate. 
Inches. 

Diameter 
of  Rivet. 
Inches. 

Diameter 
of  Hole. 
Inches. 

Single 
Riveted. 

Double 
Riveted. 

Sii,gle 
Riveted. 

Double 
Riveted. 

I 

1 

H 

o 

3 

.66 

.77 

* 

H 

3 
4 

2A 

3* 

.64 

.76 

1 

1 

51 

8* 

?i 

-  4 

.62 

.75 

A 

ii 

1 

O  :i 
-"Iff 

81 

.60 

.74 

* 

1 

if 

2| 

3* 

.58 

.73 

As  the  stress  on  the  transverse  section  is  one-half  that  on  a 
longitudinal  section,  a  single  of  double  lap  joint  is  sufficient  for 
any  ring  seam.  For  externally  fired  multitubular  boilers  with 
shell  plates  less  than  J  inch  thick,  single  riveted  ring  seams  are 
used.  For  our  boiler,  the  plates  being  ^  inch  thick,  we  will  use 
rivets  ij  inch  in  diameter,  as  this  agrees  with  good  practice. 
From  the  table,  the  pitch  for  a  |^  inch  rivet  for  single  riveted  lap 
joint  is  2Tig.  Then  as  our  ring  seam  is  3.1416  X  54  =  169.65 
inches  and  pitch  2T^  inches  we  will  have  82  +  rivets.  But  as 
we  must  have  a  whole  number  of  rivets  we  will  alter  the  pitch 
slightly  and  use  82  rivets  with  a  pitch  of  2.069  inches.  The  re- 
sult depends,  in  each  case,  upon  the  kind  of  joint  used  in  longi- 
tudinal seams.  This  merely  shows  the  general  method.  The  lap 
will  be  i£  X  I-  =  laV  incb- 


52  CONSTRUCTION  OF  BOILERS. 

For  the  longitudinal  seams  we  will  use  double  butt  joints 
with  single  riveting.  The  thickness  of  the  butt  straps  will  be 
^5gXf=.20  (nearly).  To  be  on  the  safe  side  we  will  make  the 
butt  straps  ^  inch  thick.  The  pitch  for  double  butt  joints  is 
usually  about  4  times  the  diameter  of  rivets,  so  in  this  case  it  will 
be  4x^|— 2|  inches.  We  will  use  the  same  amount  of  lap  for 
this  joint  as  for  the  lap  joint,  that  is  1^  inches. 

SECTIONS. 

The  boiler  is  made  up  of  rings  or  sections.  The  length  of 
sections  is  often  made  equal,  for  convenience  in  ordering  and 
cutting  plates.  The  length  is  limited  by  the  width  of  plate  ob- 
tainable and  the  size  of  the  riveting  machine.  This  boiler  being 
16  feet  long  would  probably  be  made  in  three  sections,  but  the 
lengths  should  be  so  adjusted  as  not  to  bring  the  ring  seam  over 
the  hottest  part  of  the  fire. 

FLUES. 

The  internal  pressure  at  which  the  boiler  shell  will  rupture 
can  be  calculated ;  but  the  external  pressure  which  will  collapse 
a  flue  can  be  determined  only  by  experiment.  External  pressure 
tends  to  increase  any  imperfection  of  shape.  For  instance,  if  a 
flue  is  slightly  oval,  the  external  pressure  tends  to  make  it  more 
flat.  The  strongest  form  to  resist  external  pressure  is  evidently 
the  circle.  When  considering  the  strength  of  flues  length  is  very 
important. 

If  a  lap  joint  is  used  the  flue  will  not  be  a  true  cylinder,  for 
this  reason  welded  or  butt  joints  are  preferable. 

Fairbain  gives  the  formula,  P  —  ' .  for  calculat- 
ing the  collapsing  pressure  of  flues,  1  —  length  of  flue  in  feet, 
d  =  diameter  in  inches,  t  =  the  thickness  in  inches,  P  —  press- 
ure per  square  inch.  The  exponent  of  t  is  often  taken  as  2 
instead  of  2.19  for  convenience.  This  formula  is  empirical  and 
was  prepared  from  his  experiments. 

C*  t^ 

Hutton  gives,  P  = __,.     In  which  C  is  a  constant,  which 

«  V  L 
is  600  for  wrought  iron  and  660  for  mild  steel,  L  =  length  iff 


60 


CONSTRUCTION  OF   BOILERS.  53 

inches,  d  =  external  diameter  in  inches,  and  t  =  thickness  in 
thirty-seconds  of  an  inch.  Results  by  Mutton's  formula  agree 
more  nearly  to  those  by  experiment  than  do  Fairbain's. 

If  the  flues  are  oval,  d  in  the  above  formula  =  the  major 
axis. 

Flues  are  strengthened  by  putting  in  hoops  at  stated  dis- 
tances. These  hoops  are  made  of  T  iron  or  angle  iron. 

TUBES. 

The  materials  for  tubes  are  iron  and  steel.  The  tubes  must 
be  tough  to  resist  cutting  by  cinders.  If  iron  is  used  it  should 
have  a  tensile  strength  of  at  least  45,000  pounds  per  square  inch, 
with  an  elongation  of  15  to  20  per  cent.  If  steel,  the  elongation 
should  not  be  less  than  26  per  cent,  when  tested  before  being  rolled. 
If  the  steel  welds  well  there  need  not  be  any  limit  to  ite  tensile 
strength.  The  ends  of  tubes  should  be  annealed  after  manu- 
facture. The  thickness  of  tubes  is  always  greater  than  that 
required  to  prevent  collapsing,  in  order  to  weld  and  expand  in 
the  tube  sheet.  It  is  often  desirable  to  use  part  of  the  tubes  as 
stays ;  for  this  purpose  the  tubes  are  made  thick  enough  to 
take  a  shallow  nut  outside  the  tube  plate. 

STAYING. 

As  large  a  portion  as  possible  of  the  shell  of  a  boiler  is  made 
cylindrical,  for  in  this  form  plates  can  be  made  sufficiently  strong 
without  the  aid  of  stays  or  braces.  But  all  flat  surfaces  must  be 
stayed ;  not  only  to  prevent  rupture,  but  also  to  provide  against 
distortion  and  grooving.  The  theoretical  investigation  of  the 
strength  of  flat  surfaces,  can  be  worked  out  only  with  higher  mathe- 
matics. From  the  formula  deduced,  the  solid  end  plate  would 
have  to  be  about  2  inches  thick  for  a  boiler  only  3  feet  in 
diameter  with  plates  |  inch  thick.  It  is  evident  that  the  flat  ends 
if  of  ordinary  thickness  must  be  strengthened  by  stays  or  braces. 
The  calculation  of  stresses  in  a  flat  plate,  supported  by  stays,  can 
be  calculated  only  when  the  supported  points  are  in  rows  thus 
dividing  the  surface  into  equal  squares.  Even  when  the  stays  are 
not  to  be  placed  in  rows  forming  squares,  it  is  well  to  make  the 
calculation  for  a  standard. 


61 


54  CONSTRUCTION  OP  BOILERS. 


The  equation  for  finding  the  area  supported  by  a  stay  rod 
is, 


in  which  a2  =  the  area  supported,  t  =  the  thickness  of  the  end 
plate,  S  =  the  allowable  stress  on  the  area  of  the  rod,  and  p  = 
the  working  steam  pressure.  Let  us  find  the  area  supported  in 
our  multitubular  boiler.  In  order  to  provide  for  future  corrosion 
we  will  use  a  factor  of  safety  of  12  and  assume,  in  the  absence  ot 
exact  knowledge,  the  ultimate  breaking  strength  of  the  rod  to  be 
60,000  pounds  per  square  inch.  It  is  usual  to  make  the  diameter 
of  the  rods  one  to  two  inches,  so  we  will  make  ours  1^  inches  in 
diameter  with  an  area  of  1.767  square  inches.  Then  the  stress 
per  rod  is  5,000  X  1.7(57  =  8,835  pounds. 


y t ~" o       y  /\  -T-  /\  w«»jf-»»y       -i  f\s\  f  •    i 

a2        _ —  — -4  =  132.5  square  inches. 

Then  as  the  rod  supports  132.5  square  inches  and  the  segment  of 
the  steam  space  is  547.2  square  inches, the  number  of  rods  will  be 

54  7-2    __    4 
1325 

The  same  formula  will  apply  in  finding  the  number  of  short 
screw  stay  bolts  of  the  fire  box. 

Suppose  we  wish  to  use  a  diagonal  or  crow  foot  stay,  making 
an  angle  of  20°  with  the  shell.  If  the  rod  is  1  inch  in  diameter 
and  the  stress  is  limited  to  7,000  pounds,  then  it  will  carry  a  pull 
of  .7854  X  7,000  =  5497.8  pounds,  and  since  it  makes  an  angle 
of  20°,  the  pull  perpendicular  to  the  head  will  be  5497.8  X  cos. 
20°  =  5497.8  X  .9397*  =  5,166  pounds.  If  the  end  is  fastened 
by  two  rivets  or  bolts  each  will  carry  2,583  pounds.  If  each  rivet 
or  bolt  supports  a  square  with  a  side  equal  to  a,  then  5,166  =  75  a2 
a2  =  £-jf-6  =68.9  square  inches  (nearly). 

*  NOTE.    Taken  from  a  table  of  cosines.  • 

UPTAKE. 

The  area  of  the  uptake,  like  the  area  of  the  tubes,  is  made 
about  j  to  I  of  the  area  of  the  grate.  We  find  that  |  of  the  grate 
surfa'ce  is  432  square  inches.  If  we  make  the  uptake  12  inches 
deep  measured  with  the  length  of  the  boiler,  it  will  be  432  -J-  12 


•       CONSTRUCTION  OF   BOILERS.  55 

=  36  inches  wide.  The  opening  of  the  shell  at  the  front  end  will 
be  12  inches  deep  and  the  plate  cut  down  until  it  is  36  inches 
wide. 

HANHOLES. 

The  manhole  and  handhole  should  be  strong  enough  and  stiff 
enough  to  sustain  the  stresses  due  to  the  direct  steam  pressure 
and  from  the  stresses  of  the  plates.  The  calculation  of  the 
strength  of  the  manhole  ring  is  difficult  and  the  results  obtained 
very  uncertain,  so  they  are  made  of  forms  and  dimensions  that 
have  been  used  in  good  practice  and  given  good  results.  These 
fittings  are  bought  in  steel  forgings.  Boiler  makers  design  the 
forged  rings  which  lie  close  to  the  shell,  of  a  section  at  least  equal 
to  the  ^section  of  the  plate  that  is  cut  out.  The  bearing  surfaces 
of  the  manhole  cover  and  that  of  the  lip  against  which  the  cover 
bears,  should  be  machined  to  make  a  good  smooth  joint.  The 
joints  are  made  tight  by  gaskets  about  |  of  an  inch  wide. 

Hand  holes  are  constructed  similarly  to  manholes,  and  often 
have  a  taper  key  in  place  of  a  bolt  and  nut.  because  the  nut  is 
exposed  to  fire  and  after  it  has  been  in  place  pome  time,  is  often 
difficult  to  remove  with  a  wrench. 

BRACKETS. 

Boilers  of  the  multi  tubular  types  are  supported  by  brackets 
usually  made  of  cast  iron.  Boilers  up  to  16  feet  long  have  four 
brackets  and  those  more  than  16  feet  long  have  six  brackets.  The 
brackets  for  this  boiler  should  be  about  10  inches  long,  measured 
with  the  length  of  the  boiler,  and  about  15  inches  wide.  They  are 
riveted  to  the  boiler  with  nine  or  ten  rivets  |  to  1  inch  in  diame- 
ter. The  rivets  can  be  made  large,  as  a  large  rivet  makes  a  strong 
joint,  and  in  this  case  the  pitch  is  not  governed  by  calking. 

The  load  on  the  brackets  can  be  estimated  by  calculating  the 
weight  of  the  boiler  full  of  water  and  adding  the  weight  of  all  the 
parts  supported  by  the  boiler.  These  parts  include  pipes,  valves, 
jauges,  brickwork  covering,  etc.  This  load  should  be  divided  as 
nearly  equal  as  possible  among  the  four  brackets,  so  that  the 
tendency  of  the  boiler  toward  bending  shall  be  small. 


63 


56  CONSTRUCTION  OF  BOILERS. 

Brackets  are  set  above  the  middle  line  of  the  boiler  in  order 
that  the  flanges  may  be  protected  by  the  brickwork  setting.  They 
are  usually  3  or  4  inches  above  the  middle. 

CHinNEYS, 

At  the  present  time,  the  knowledge  of  chimneys  and  chimney 
draft  is  slight.  The  theories  given  are  worth  but  little  as  they 
are  based  upon  data  which  is  entirely  insufficient.  As  to  the 
design  and  proportions  of  chimneys,  there  are  no  systematic 
statements  and  rules  that  can  be  used. 

Chimneys  are  usually  designed  from  empirical  formulas  and 
from  tables,  compiled  from  proportions  of  chimneys  that  have  fur- 
nished sufficient  draft,  etc. 

The  draft  produced  in  a  chimney  is  due  to  the  difference  in 
temperature,  and  consequently  difference  in  pressure,  between  the 
gases  inside  the  chimney,  and  the  air  outside.  The  gases  in  the 
chimney  being  lighter  rise  toward  the  top  and  air  rushes  in  at 
the  bottom  to  fill  the  space  left  by  the  hot  gases.  This  air  as  it 
becomes  heated  grows  lighter  and  rises,  thus  a  continuous  circula- 
tion is  kept  up.  The  temperature  of  the  gases  in  the  chimney  is 
considered  to  be  about  600°  F.  for  chimney  calculation,  as  practice 
shows  this  to  give  good  draft  under  economical  conditions. 

After  making  several  assumptions,  based  on  experiments,  the 
following  formula  has  been  deduced : 

H.  P.  =  3.33  (A  —  .6  v/AT)  v'h" 

in  which  H.  P.  =  horse-power,  A  =  area  of  the  chimney,  and  h 
=  the  height  above  the  grate. 

The  following  table  on  page  46  has  been  calculated  from  this 
formula.  This  table  is  used  to  a  considerable  extent  with  satis- 
factory results. 

The  part  of  the  table  which  is  used  for  ordinary  proportions 
is  filled  in.  If  proportions  are  taken  from  the  table  rather  than 
from  the  formula,  the  results  will  give  better  proportions. 

To  find  the  area  of  the  top  of  the  chimney  for  a  given  coal 
consumption,  the  following  empirical  formula  has  been  stated, 

A    _  H.  P.  X  B  X  12 

A—    ~ 


64 


CONSTRUCTION  OF  BOILERS. 


57 


in  which  A  =  area,  H.  P.  =  horse-power  of  boiler,  B  =  number 
of  pounds  consumed  per  H.  P.  per  hour  and  h  =  height  of 
chimney  in  feet. 

This  area  A  is  the  area  in  square  inches  at  the  top. 


g  3 

HEIGHT  OF  CHIMNEYS  AND  COMMERCIAL  HORSE-POWER. 

is 

rg 

ti 

jjl 

f! 

III 

c3*M 

11 

50 

60 

70 

80 

90 

100 

110 

125 

150 

175 

200 

55 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

ft. 

Is 

W  JJ 
03 

II 

18 

23 

25 

27 

16 

0.97 

1.77 

21 

35 

38 

41 

19 

1.47 

2.41 

24 

49 

54 

58 

62 

22 

208 

3.14 

27 

65 

72      78 

83 

24 

2.78 

3.98 

30 

84 

92    100 

107 

113 

27 

3.58 

4.91 

33 

115    125 

133 

141 

30 

4.48 

5.94 

36 

141    152 

161 

173 

182 

32 

5.47 

7.07 

39 

183 

196 

208 

219 

35 

6.57 

8.30 

42 

210 

231 

245 

258 

271 

38 

7.76 

9.62 

48 

311 

330 

348 

365 

389 

43 

10.44 

12.57 

54 

427 

449 

472 

503 

551 

48 

13.51 

15.90 

60 

536 

565 

593 

632    692 

748 

54 

16.98 

19.64 

66 

694 

728 

776!  849 

918 

981 

5'J 

20.83 

23.76 

72 

835 

876 

934  1023 

1105 

1181 

64 

25.08 

28.27 

78 

1038 

11071212 

1310 

1400 

70 

29.73 

33.18 

84 

1214 

1294  1418 

1531 

1637 

75 

34.76 

38.48 

90 

1496  1639 

1770 

1893 

80 

40.19 

44.18 

96 

1876 

2027 

2167 

86 

46.01 

50.27 

Another  method  which  is  much  more  simple  is  to  design  the 
area  of  the  chimney,  as  we  have  designed  the  total  tube  area  ;  that 
is,  about  ^  the  grate  area.  This  ratio  for  chimneys  is  sometimes 
about  ^  and  decreases  to  1  and  for  very  tall  chimneys  to  -Jj. 

From  the  table  we  find  the  chimney  to  have  an  area  at  the 
top  of  about  3.98  square  feet,  assuming  it  to  be  60  or  70  feet 
high.  This  area  gives  a  diameter  of  27  inches  if  circular,  or  24 
inches  if  square. 


Let  us  calculate  it  from  the  formula  A  = 


P.  X  B  X  12 

V/h 


We  must  either  assume  or  calculate  B.  As  the  calculation 
is  very  easy  it  would  be  better  than  any  assumption.  The  total 
amount  of  coal  burned  per  hour  equals  12  X  24  or  288  pounds. 
The  amount  per  H.  P.  per  hour  is  288  ~  75  or  3.84  pounds. 


58  CONSTRUCTION  OF  BOILERS. 

Then  assuming  the  chimney  to  be  60  feet  high, 

A        75  X  3.84  X  12  ,      ,    0. 

A  =  -  —  -  -  =  44o    square    inches,    or   about    24 


inches  in  diameter  if  circular  and  21  inches  if  square. 

By  the  last  method  the  area  of  the  chimney  will  be  24-4-8 
or  3  square  feet,  or  432  square  inches,  giving  practically  the  same 
result  as  with  the  formula. 

As  the  table  is  reliable  and  gives  us  the  larger  area,  we 
will  use  it  and  be  on  the  safe  side  ;  also  as  the  amount  of  coal 
burned  per  hour  by  the  draft  in  a  chimney  can  be  found  by  mul- 
tiplying the  horse-power  in  the  above  table  by  5,  the  chimney 
with  an  area  of  3.98  square  feet  and  60  feet  high  will  burn 
72  X  5  =  360  pounds  of  coal  per  hour.  The  boiler  in  question 
burns  only  288  pounds,  so  the  chimney  is  sufficiently  large. 

Chimneys  are  usually  of  brick  or  of  steel  plates.  If  of  steel 
they  are  always  circular.  When  made  of  brick  they  are  circular, 
square  or  hexagonal.  With  a  given  draft  area,  a  circular  chimney 
requires  the  least  material,  since  a  circumference  has  the  least 
perimeter  for  a  given  area  ;  it  also  presents  less  resistance  to  wind. 

A  steel  chimney  is  made  up  of  plates  of  steel  riveted  to- 
gether. The  shell  is  bolted  through  a  foundation  ring  of  cast  iron 
to  the  stone  foundation.  It  has  a  straight  taper  to  the  top,  which 
is  finished,  for  appearance  with  light  plates.  The  shell  is  lined 
with  fire-brick,  with  a  thickness  which  varies  from  12  to  18  inches 
at  the  bottom  to  about  2  to  4  inches  at  the  top.  This  lining  is 
used  to  prevent  heat  being  lost  from  the  shell  and  does  not  add  to 
the  strength  of  the  chimney. 

A  brick  chimney  is  built  in  two  parts  ;  a  the  outer  shell, 
which  resists  wind  pressure  and  5,the  lining  which  is  the  flue. 
This  flue  is  made  separate  from  the  external  shell  in  order  that  it 
may  expand,  when  the  chimney  is  full  of  hot  gases,  without  strain- 
ing the  outer  shell. 

The  interior  of  both  steel  and  brick  chimneys  are  often  cylin- 
drical while  the  exterior  tapers.  The  taper  is  about  .3  inch  to 
the  foot.  The  brick  at  the  base  of  the  chimney  is  splayed  out  to 
make  a  large  base.  , 


66 


,  CONSTRUCTION  OF  BOILERS. 


As  good  natural  earth  should  carry  from  2000  to  4000  pounds 
per  square  foot,  the  base  of  the  chimney  should  be  large  enough 
so  that  this  pressure  will  not  be  exceeded. 

The  external  shell  is  calculated  for  wind  pressure  and  the 
weight  of  brick.  This  calculation  for  wind  pressure  involving 
higher  mathematics  will  not  be  treated  here.  The  lining  is  cal- 
culated for  compression  due  to  weight.  The  design,  both  of  the 
chimney  and  its  foundation,  should  be  made  by  a  competent  engi- 
neer of  experience,  on  account  of  disastrous  results  should  a 
chimney  fall. 


67 


!i 


TYPES  OF  BOILERS, 


Generally  speaking,  a  steam  boiler  is  a  closed  metallic  vessel 
in  which  steam  is  generated  from  water  by  the  application  of  heat. 
As  steam  is  under  pressure  it  is  evident  that  the  vessel  must  be 
strong  and  tight. 

To  operate  the  boiler  safely  and  economically  there  must  be 
certain  fittings  and  accessories — some  of  these  are  used  in  the  care 
of  the  boiler,  while  others  serve  to  increase  the  economy.  Among 
the  most  important  attachments  and  appurtenances  may  be  men- 
tioned the  following: 

A  feed  pump  or  injector,  with  valves,  piping,  etc.,  to  supply 
water  to  the  boiler. 

Gage  cocks  and  glass  water  gage  to  show  the  attendant  the 
height  of  water  or  the  water  level,  as  it  is  called,  in  the  boiler. 

A  pressure  gage  to  show  the  pressure  of  steam  in  the  boiler. 
The  pressure  is  usually  measured  in  pounds  per  square  inch. 

A  safety  valve  to  allow  steam  to  escape  from  the  boiler  when 
the  pressure  exceeds  a  certain  fixed  amount.  This  attachment, 
being  a  safety  device,  should  be  automatic  and  reliable. 

A  blow=off  pipe,  with  its  valves,  to  blow  out  sediment  from 
the  boiler,  reduce  the  amount  of  water  in  the  boiler,  or  empty  it. 

A  steam  pipe,  with  its  valves,  to  conduct  the  steam  from  the 
boiler  to  the  place  where  it  is  to  be  used. 

Manholes  and  handholes,  with  covers,  for  examination,  re- 
pairs, and  cleaning. 

*  Fusible  plugs  to  give  warning  when   the  water  level  be- 
comes too  low,  or  melt  and  allow  the  water  to  escape. 

*  High=  and   low-water  alarms  to  give  warning  when   the 
water  level  is  too  high  or  too  low. 

*  A  heater  to  raise  the  temperature  of  the  feed  water  as  nearly 
as  possible  to  that  of  the  water  in  the  boiler. 


*NOTE.    Although  the  last  three  are  desirable,  they  are  not  abso- 
lutely necessary j  PS  a  boiler  can  be  successfully  operated  without  them. 


TYPES  OF   BOILERS 


In  addition  to  these  there  are  other  attachments  such  as: 

Lugs  or  brackets  for  supporting  the  boiler. 

Masonry  for  setting  the  boiler  and  keeping  it  in  position,  and 
in  many  cases  to  keep  the  hot  gases  in  contact  with  the  shell. 

Furnace  fittings,  including  grate  bars,  bearer  bars,  dampers, 
fire  doors,  ashpit  doors,  etc. 

The  chimney  to  carry  away  the  waste  gases  and  create  draft. 

Tools,  such  as  shovels,  slice  bars,  scrapers,  tube  brushes,  etc. 

DEFINITIONS. 

The  following  definitions  should  be  remembered  in  connec- 
tion with  the  terms  used  in  designating  the  various  classes. 

A  fire=tube  boiler  is  one  having  the  heating  surface  composed 
largely  of  tubes  which  are  surrounded  with  water,  the  hot  gases 
passing  through  them. 

A  water=tube  boiler  is  also  composed  of  tubes,  but  in  this 
case  water  flows  through  the  tubes,  while  the  hot  gases  pass  around 
and  among  them. 

In  a  sectional  boiler  the  tubes  and  corresponding  headers 
form  comparatively  small  units.  Each  unit  is  complete  in  itself; 
that  is,  it  is  in  communication  with  a  steam  and  water  drum  but 
is  independent  of  the  other  units. 

A  non=sectional  boiler  is  one  having  all  the  tubes  in  com- 
munication with  one  another;  in  other  wrords,  all  or  nearly  all  the 
tubes  are  expanded  into  a  common  header  or  drum.  The  boiler  is 
not  made  up  of  units. 

A  single=tube  boiler  is  made  up  of  plain  tubes. 

A  double  tube  boiler  has  a  small  tube  inside  of  the  regular 
tube  and  concentric  with  it. 

A  boiler  is  externally=fired  when  the  furnace  is  separate  from 
the  shell;  in  such  boilers  the  fire  is  usually  placed  in  a  brick 
furnace.- 

In  the  internally=fired  boiler  the  grate  is  inside  of  a  flue 
which  is  within  the  shell. 

A  fire-box  boiler  is   one   having   the   fire   within   a   fire   box 

O 

which,  although  external  to  the  shell,  is  rigidly  connected  to  it. 
The  fire  box  is  usually  made  of  steel  places  instead  of  brick  as  in 
the  case  of  the  externally-fired  boiler. 


70 


TYPES  OF  BOILERS 


CLASSIFICATIONS. 

The  almost  endless  variety  of  boilers  now  in  use  is  due  largely 
to  the  many  conditions  under  which  they  are  used.  Other  reasons 
for  the  numerous  forms  are  the  great  latitude  in  design  and  con- 
struction, and  the  competition  among  engineers,  who  have,  during 
the  last  century,  sought  to  produce,  at  moderate  cost,  steam  gener- 
ators that  will  be  safe,  durable,  and  economical. . 

The  necessity  for  careful  classification  before  discussing  the 
details  is  apparent  when  one  considers  the  similarities  and  differ- 
ences. Much  valuable  time  may  be  saved  by  selecting  some  make 
of  boiler  to  represent  a  given  class.  Still  further,  the  classifica- 
tion reduces  the  chances  of  overlooking  interesting  features. 

CLASSIFICATION. 
According  to  Use. 


C  Early  Forms. 
Plain  C 


Stationary 


Jylindrical 
Single  Flue,  Externally-fired 

(  Cornish  (single-flue) 
FlueBoilers-j  Lancashire  (two-flue) 
(  Galloway 

M.l«ubul« 


Straight-tube 
Curved-tube 


flarine 


Sectional 
I  Non-sectional 
Mixed  Types 
I  Peculiar  Forms 

Early  Forms  (box  or  rectangular) 

Scotch  or  Drum 

Return-tube 

Through-tube 

Curved-tube 
Straight-tube 
Sectional 
Non-sectional 

Launch  Boilers 


Water-tube 


SMultitubular  fire-box  (common  form) 
Wooten  Type 
Corrugated  Furnace 
Peculiar  Forms 

Boilers  may  be  classified  in  many  ways.     They  may  be  divided 
into  the  following  great  classes:  Fire-tube  and  water-tube,  vertical 


71 


TYPES  OF  BOILERS 


and  horizontal,  stationary  and  non-stationary,  or  externally-fired 
and  internally-fired.  They  may  also  be  classified  according  to  uses 
or  according  to  forms  of  construction.  For  illustration,  two  classi- 
fications, of  which  the  following  seems  better  for  this  discussion, 
are  given. 

CLASSIFICATION. 
According  to  Form  of  Construction. 

Early  Forms. 

f  Cornish  (single-flue) 
r,,       )  Lancashire  (two-flue) 
Flue]  Galloway 

(Single  Flue  (externally-fired) 


Horizontal  (common  form) 

Vertical 

Return-tube 

Through-tube 

Fire-box 

Peculiar  Forms 


Fire=tube 

(Multitubular) 


f  Horizontal  j 

Water=tube^   Vprtl>al      (  Straight-tube 
Vertical      j  Curved-tube 
I  Peculiar  Forms 

Mixed  Types. 

EARLY    FORMS. 

The  earliest  boilers  of  which  we  have  reliable  record  were 
spherical.  They  were  of  cast  iron  and  set  in  brickwork.  It  was 
customary  to  set  this  type  of  boiler  with  the  fire  underneath  and 
construct  flues  in  the  brickwork  to  conduct  the  hot  gases  around 
the  boiler  just  below  the  water  level.  The  hot  gases  passed  entirely 
around  the  boiler  before  escaping  to  the  chimney. 

The  Haystack  Boiler.  The  next  form  to  be  generally  used 
was  that  invented  by  Newcomen  in  1711.  On  account  of  its  pecul- 
iar shape  it  was  called  the  "  Haystack  "  or  "  Balloon  "  boiler.  It 
was  of  wrought  iron  and  had  a  hemispherical  top  and  arched  bot- 
tom. The  fire  was  placed  underneath  the  arched  portion;  the  hot 
gases  surrounding  the  lower  part  of  the  boiler.  An  improved  form 
of  the  Haystack  boiler  is  shown  in  Fig.  1.  Smeaton  placed  the 
fire  inside  the  shell  and  arranged  internal  flues  for  conducting 


72 


TYPES  OF  BOILERS 


the  hot  gases  to  the  chimney.      This  arrangement  increases  the 
heating  surface  and  consequently  the  economy  of  the  boiler. 

The  Wagon  Boiler.  To  still  further  increase  the  heating  sur- 
face, James  Watt  introduced  his  "Wagon"  boiler.  This  form  is 
shown  in  Fig.  2.  The  top  was  cylindrical  and  the  sides  curved 
inward.  The  curved  plates  as- 
sisted in  the  formation  of  flues 
on  either  side.  The  hot  gases 
passed  from  the  grate,  under- 
neath the  boiler  to  the  rear, 
through  the  left-hand  flue  to  the 
front,  then  through  the  right- 
hand  flue  to  the  rear  and  thence 
to  the  chimney.  This  was  called 
the  wheel  draft  because  the 
gases  passed  entirely  around  the 
boiler.  In  the  large  sizes  a  flue 
was  placed  in  the  boiler.  The 
products  of  combustion  returned 
through  this  flue  to  the  front 
after  passing  under  the  boiler  to 
the  rear,  as  in  the  small  sizes. 
On  issuing  from  the  flue  at  the 
front,  the  gases  divided  and  Fig.  1. 

passed  to  the    chimney   at    the 

rear  by  means  of  the  flues  in  the  brickwork.     This  form  of  draft 
was  called  the  split  draft. 

Watt  used  a  column  of  water  in  the  vertical  feed  pipe  as  a 
pressure  gage;  the  rise  and  fall  of  this  column  also  controlled  the 
damper.  The  feed  was  regulated  by  a  float. 

MODERN  BOILERS. 

Although  such  boilers  as  the  Haystack,  Wagon,  and  others  were 
fairly  satisfactory  in  the  period  in  which  they  were  invented,  they 
could  not  stand  the'  higher  pressures  that  soon  became  common. 

About  the  beginning  of  the  nineteenth  century  the  cylindrical 
boiler  was  introduced.  The  earliest  forms  were  the  plain  cylin- 
drical boiler  and  the  "  Egg-end "  boiler.  The  difference  was  in 


73 


TYPES  OF  BOILERS 


the  form  of  the  ends  —  those  of  the  former  were  flat  and  of  cast 
iron,  while  the  ends  of  the  latter  were  hemispherical  and  made  oi 
wrought  iron.  The  egg-end  boiler  required  no  staying  or  bracing 
because  its  form  is,  with  the  exception  of  a  sphere,  the  strongest 
to  resist  internal  pressure. 

The  Cylindrical  Boiler  consisted  of  a  shell  of  wrought-iron 
boiler  plate  and  ends  of  the  same  material  or  of  cast  iron.     It  was 


set  in  brickwork  as  shown  in  Fig.  3.  The  boiler  was  about  two- 
thirds  filled  with  water,  the  remaining  third  forming  the  steam 
space.  To  collect  and  store  the  steam  as  it  rose  from  the  water  a 
steam  dome  was  added.  The  steam  pipe  was  attached  to  the  dome 
to  wrhich  the  safety  valve  also  was  connected.  The  hot  gases  from 
the  fire  passed  under  the  boiler  to  the  rear  and  then  to  the  chimney. 


74 


CROSS  SECTION  OF  WHEELER  WATER-TUBE  BOILER 
300  Horse  Power,  Arranged  for  Blast  Furnace  Gas. 


TYPES  OF  BOILERS 


The  heating  surface  of  this  type  is  small  with  a  given  diam- 
eter unless  the  boiler  is  made  very  long.  As  all  sediment  collects 
in  the  bottom,  where  the  heat  is  most  intense,  the  plates  are  liable 
to  burn.  Since  sediment  and  scale  are  poor  conductors  of  heat, 
the  heat  remains  in  the  plates  and  overheats  them  instead  of  flow- 
ing to  the  water. 

The  disadvantages  (the  small  heating  surface  and  the  collec- 
tion of  sediment)  do  not  seem  so  serious  when  one  considers  the 


Fig.  3. 

simplicity  of  construction,  strength,  durability,  and  ease  of  repair- 
ing and  cleaning. 

The  plain  cylindrical  boiler  was  adapted  for  mining  districts, 
iron  works  and  other  places  where  fuel  is  abundant  and  skilled 
boiler  makers  are  not  readily  found.  This  boiler  was  made  very 
long  to  get  the  required  heating  surface,  the  length  sometimes 
exceeding  fifty  feet. 

FLUE  BOILERS. 

In  order  to  get  the  necessary  heating  surface  in  the  cylindrical 
boiler  without  making  it  excessively  long,  it  was  made  with  an 
internal  flue  through  which  the  hot  gases  passed  to  the  chimney. 
This  flue  was  quite  large  and  extended  from  end  to  end.  In  the 


75 


10 


TYPES  OF  BOILERS 


United  States,  Oliver  Evans  used  this  type  in  1800.  In  England, 
it  led  to  the  internally-flred  flue  boilers  which  were  so  extensively 
used. 

THE  CORNISH  BOILER. 
Horizontal— Single-Flue— Internally-Fired. 

When  it  was  found  that  about  25  per  cent  of  the  total  heat  of 
combustion   was  lost  by  radiation  from   the    furnace,  a  Cornish 


Fig.  4. 

engineer  named  Trevithick,  conceived  the  idea  of  placing  the  lire 
inside  the  large  internal  flue.     He  introduced  this  type  which  is 

known  as  the  Cornish  boiler. 

The  products  of  combustion 
pass  from  the  fire  on  the  grate 
bars  C  (Fig.  4)  through  the  flue 
to  the  back  end  where  they  divide 
and  return  to  the  front  end  by 
means  of  the  lateral  flues  L  in  the 
brickwrork.  See  Fig.  4^.  At  the 
front  the  hot  gases  pass  down- 
ward, and  uniting  pass  through 
the  flue  F  in  contact  with  the  bot- 
torn  of  the  boiler.  On  leaving 
the  boiler  they  go  to  the  chim- 
ney. This  arrangement  of  flues  reduces  the  temperature  of  the 
gases  before  they  come  in  contact  with  the  bottom  of  the  boiler 
where  sediment  collects.  The  grate  bars  rest  on  the  dead  plate  D 


4 


76 


TYPES  OF  BOILERS 


11 


at  one  end  and  on  the  bridge  13  at  the  other;  if  made  in  two  lengths 
(as  is  often  the  case)  they  are  supported  at  the  center  by  a  cross  bearer. 
The  bridge  is  built  of  lire  brick  and  the  external  flues  are  lined  with 
fire  brick.  The  heads  are  stayed  to  the  shell  by  gusset  stays  E  E. 

The  large  internal  flue 
is  the  hottest  portion  of  the 
boiler  because  it  contains  the 
tire.  For  this  reason  the  flue 
has  greater  linear  expansion 
than  the  shell  and,  if  the  flue 
is  a  plain  cylinder,  the  in- 
crease in  length  causes  the 
ends  to  bulge.  When  the 
boiler  is  cold,  the  flue  re  turns  to  its  normal  length.  This  lengthen- 
ing and  shortening  will  soon  loosen  the  flue  at  the  ends.  To  over- 
come this,  the  flue  is  sometimes  made  up  of  several  short  rings 
flanged  at  the  ends  and  joined  by  being  riveted  to  a  plain  ring. 
This  construction  is  shown  in  section  in  Fig.  4.  Another  method 


Fig.  6. 

is  shown  in  section  in  Fig.  5.  The  plain  ring  is  riveted  to  the 
curved  ring;  this  ring  takes  up  the  expansion,  increases  the  heat- 
ing surface,  and  strengthens  the  flue  against  external  pressure. 
The  same  results  may  be  obtained  by  the  use  of  the  corrugated 
flue,  one  form  of  which  is  shown  in  Fig.  6.  The  corrugated  flue 
has  many  advantages  over  the  devices  shown  in  Figs.  4  and. 5;  it  is 
frequently  used  in  marine  boilers. 

LANCASHIRE  BOILER. 
Horizontal—  Two=Flue— Internal!y=Flred. 

It  can  be  proved,  both  by  experiment  and  calculation,  that 
with  a  given  thickness  large  cylinders  cannot  stand  aa  much  ex- 


7Y 


12 


TYPES  OF  BOILERS 


ternal  pressure  as  small  ones.  For  this  reason  and  on  account 
of  the  short  distance  a  fireman  can  throw  coal  accurately,  the 
Cornish  boiler  is  suitable  for  small  powers  only.  If  it  is  made  too 
large,  the  flue  is  liable  to  collapse,  but  if,  on  the  other  hand,  the 
flue  is  of  too  small  a  diameter,  the  grate  will  be  insufficient.  If 
this  form  of  boiler  is  to  be  used  in  large  size  it  is  modified  by 
using  two  flues  instead  of  one.  This  boiler  is  called  the  Lanca- 


Fig.  7. 

shire  boiler.  It  is  like  the  Cornish  type  except  that  it  has  two 
flues  and,  of  course,  two  furnaces. 

The  flues  are  sometimes  continued  separately  to  the  end.  If 
they  merge  into  one  large  flue,  which  forms  the  combustion  cham- 
ber, it  is  called  the  "  Breeches-flued  "  or  duplex  furnace  boiler. 
These  furnaces  are  fired  alternately;  the  un burned  gases  set  free 
from  the  freshly-fired  coal  are  burned  on  meeting  the  hot  gases  from 
the  incandescent  coal  of  the  other  furnace.  This  arrangement 
prevents  the  escape  of  the  unburned  hydrocarbons. 

The  disadvantage  of  the  Lancashire  boiler  is  the  difficulty  in 
finding  room  for  the  two  flues  without  greatly  increasing  the  diam- 
eter of  the  boiler.  Also,  the  small  furnace  is  unfavorable  to  com- 


78 


TYPES  OF  BOILERS 


plete  combustion  as  the  space  for  the  uniting  and  burning  of 
the  hydrocarbons  is  restricted.  The  combustion  chamber  of  the 
breeches -flued  boiler  provides  the  necessary  space,  but  the  construc- 
tion at  the  junction  of  the  two  flues  is  weak  and  has  been  the 
cause  of  many  explosions. 

GALLOWAY  BOILER. 
Horizontal—  Two=Flue— InternalIy=Fired— Galloway  Tubes. 

Another  boiler  of  the  same  gen- 
eral form  is  the  Galloway,  shown 
in  Fig.  7.  This  boiler  differs  from 
the  Lancashire  in  that  short  tubes 
are  added  to  the  flues.  In  the  Gallo- 
way boiler  having  two  distinct  flues, 
the  tubes  were  placed  as  shown  in 
Fig.  8. 

In  the  later  form  of  Galloway 
boiler,  the  two  flues  merge  into  one 
large  flue  of  the  shape  shown  in 
Fig.  9.  This  flue  has  corrugated 
sides  and  the  conical  tubes  are  staggered,  thus  insuring  a  thor- 
ough breaking  up  of  the  currents  of  hot  gases.  The  tubes  are 


Fig.  8. 


Fig.  9. 


made  conical  to  facilitate  removal  for  repairs.     The  shape  of  the 
tube  also  permits  the  water  to  expand  on  being  heated,  and  the  par- 


70 


14 


TYPES  OF  BOILERS 


tides  rise  vertically  without  disturbing  the  water  on  the  heating 
surfaces  above.  The  conical  tubes  are  generally  riveted  rather 
than  welded  because  the  removal  of  a  tube  that  is  welded  leaves  a 
large  hole  in- the  flue. 

FIRE-TUBE  BOILERS. 

SINGLE=FLUE   BOILER. 

Horizontal^Single  Fire  Tube— Externally-Fired. 

In   the  Cornish,  Lancashire,  and   Galloway  boiler    the  large 
internal   flue   served  as  a  fire    box.     There  was,  however,  a  flue 


Fig.  10. 

boiler  having  the  lire  external  to  the  shell.  The  boiler  shown  in 
Fig.  10  resembles  the  plain  cylindrical  boiler  both  in  appearance 
and  setting,  but  it  has  one  or  more  large  flues  extending  from  end 
to  end.  This  flue  increases  the  heating  surface  to  such  an  extent 
that  the  boiler  can  be  considerably  shorter  than  the  plain  cylin- 
drical. 

MULTITUBULAR   BOILER. 
Horizontal— Many  Small  Fire  Tubes— Externally-Fired. 

When  engineers  found  that  the  internal  flue  was  such  an 
advantage  (that  is,  it  increased  the  heating  surface),  they  soon 
added  more  tubes;  as  the  number  increased,  the  size  diminished 
until  they  became  of  the  size  used  at  present.  This  is  in  brief  the 


TYPES  OF  BOILERS 


15 


development  of  the  multitubular  boiler.  This  type  of  boiler  has 
for  many  years  been  commonly  used  for  stationary  work  and 
although  other  types  possess  ad  vantages  for  certain  conditions,  it  is 
still  considered  economical,  reliable,  easily  handled,  and  safe  if  con- 
structed of  good  material  and  operated  with  care  and  intelligence. 
Figs.  11  to  14  are  selected  to  illustrate  this  boiler.  The  boiler 
without  the  brick  setting  is  shown  in  Fig.  11.  It  consists  of  a 


Fig.  11. 

steel  cylindrical  shell  and  numerous  small  tubes  extending  from 
end  to  end.  These  tubes  are  3  or  4  inches  in  diameter  and  are 
fastened  to  the  two  ends  (called  tube  -sheets)  by  expanding  the 
tubes  against  the  sheet  and  beading  them  over  on  the  outside. 
The  shell  is  made  of  steel  plates  ^  to  |-inch  in  thickness.  At  the 
front,  the  shell  plates  extend  beyond  the  tube  sheet  and  are  cut 
away  to  allow  the  waste  gases  to  enter  the  uptake.  About  one- 
third  the  volume  of  the  boiler  is  occupied  by  the  steam;  the  other 
two-thirds  is  filled  with  water  and  tubes.  The  water  line  is  a  little 
(from  4  to  8  inches)  above  the  top  row  of  tubes. 

The  flat  ends  are  prevented  from  bulging  by  stays  \vhich  may 
be  of  the  form  shown  in  Fig.  12  or  they  may  be  diagonal  stays. 
The  through  stays  are  fastened  to  the  tube  plates  by  means  of  nuts 
and  washers  as  shown  at  S  in  Fig.  11,  and  also  in  Fig.  12.  Below 
the  water  level,  the  end  plate  is  stayed  by  the  tubes.  This  type  of 
boiler  may  be  supported  by  brackets  B  riveted  to  the  shell  or  by 
means  of  beams  and  columns,  as  shown  in  Fig.  14.  The  front 
bracket  is  often  fixed  in  the  side  wall,  but  the  rear  bracket  should 
be  placed  on  rollers  so  that  it  can  move  on  an  iron  plate.  This 


81 


16 


TYPES  OF  BOILERS 


TYPES  OF  BOILERS 


17 


will  prevent  the  straining  of  the  plates  from  expansion  and  con- 
traction. A  small  space  must  be  left  between  the  rear  tube  sheet 
and  the  brick  wall  to  allow  for  expansion. 

The  boiler  shown  in  Fig.  11  has  two  steam  nozzles  X.  If  the 
boiler  has  a  dome  (D  Fig.  13)  the  steam  nozzle  is  at  or  near  the  top 
of  the  dome.  The  feed  pipe  may  enter  either  at  the  front  or  at 
the  rear.  It  frequently  terminates  in  a  perforated  pipe  below  the 
water  line.  The  blow-off  pipe  is  at  the  rear  of  the  boiler  as  shown 


Fig.  13. 

in  Fig.  13  A  valve,  called  the  blow-off  valve,  regulates  the  flow 
and  may  be  opened,  when  there  is  low  pressure  in  the  boiler,  co- 
blow  out  sediment  and  detached  scale.  The  boiler  is  usually  set 
with  a  slight  inclination  towrard  the  rear  so  that  mud  and  detached 
scale  may  collect  near  the  blow-off  pipe. 

In  order  that  the  boiler  may  be  entered  for  cleaning  or  repairs, 
it  is  provided  with  manholes  and  handholes.  Fig.  11  shows  a 
manhole  M  at  the  top  near  the  middle  and  a  handhole  near  the 
bottom  of  the  front  tube  sheet.  Handholes  may  be  put  in  wherever 
desired,  but  manholes  can  be  located  only  where  the  arrangement 
of  stays  and  tubes  will  permit  the  entrance  of  a  man.  Manholes 
and  handholes  are  elliptical;  the  former  being  about  11  inches  by 
15  inches  in  size;  while  the  latter  are  about  4  inches  by  6  inches. 


L8 


TYPES  OF  BOILERS 


84 


TYPES  OF  BOILERS 


ig 


The  heating  surface  is  the  surface  in  contact  with  the  hot 
gases.  In  this  type,  the  heating  surface  is  made  up  of  about  half 
the  shell,  the  tubes,  and  about  two-thirds  of  the  rear  tube  sheet. 
In  general,  all  the  heating  surface  is  belowr  the  wrater  line. 

The  complete  multitubular  boiler  is  shown  in  its  brick  setting 
in  Fig.  14,  and  a  longitudinal  section  of  the  setting  in  Fig.  13. 
The  brick  setting  consists  of  brick 
laid  in  cement  or  mortar.  The 
bridge  and  the  portions  of  the  fur- 
nace exposed  to  the  fire  are  lined 
with  fire  brick.  The  bridge  is  built 
at  the  rear  of  the  grate  and  forms  a 
support  for  the  grate  bars;  it  also  di- 
rects the  flames  upward.  The  arrows 
show  the  direction  of  the  flow  of  hot 
gases.  The  furnace  is  formed  by 
the  bridge,  the  side  walls,  and  the 
lower  part  of  the  boiler  front.  The 
boiler  front  is  usually  cf  cast  iron 
with  the  lower  part  lined  with  fire 
brick.  The  front  has  doors  which 
lead  to  the  furnace,  ashpit,  and 
smoke  box.  The  space  below  the 
grate  is  called  the  ashpit,  and  through 
its  doors  ashes  are  removed  and  a 
large  portion  of  the  air  for  combus- 
tion enters.  Both  the  fire  doors  and 
ashpit  doors  have  draft  plates,  or 
grids,  to  regulate  the  supply  of  air. 


Fig.  15. 

The  doors  to  the  smoke  box 
give  access  to  the  tubes  for  cleaning  and  repairs. 


UPRIGHT  BOIL"°S. 
Vertical—  Many  Small  Fire  Tubes—  Fire  Box. 

Upright  boilers  are  used  when  floor  space  is  valuable  and 
there  is  sufficient  height.  In  small  sizes,  they  are  used  for  hoist- 
ing engines,  pile  driving,  for  supplying  steam  for  pumps,  and 
similar  work;  in  large  sizes  when  it  is  necessary  to  have  a  powerful 
battery  in  a  small  space.  In  general  *hey  are  not  as  economical  as 


85 


20 


TYPES  OF  BOILERS 


the  horizontal  multitubular  boiler  unless  they  are  carefully  designed 
and  of  considerable  height.  If  the  tubes  are  short,  the  hot  gases 
escape  before  they  give  up  much  of  their  heat. 

One  of  the  simplest  forms  of  upright  boiler  is  shown  in  Fig. 
15.  It  has  a  cylindrical  shell  with  a  large  fire  box  at  its  lower 
end.  This  fire  box  is  formed  by  the  inner  cylinder  which  is  fas- 
tened to  the  outer  shell  by  short  screw  stay  bolts  as  shown.  A 


Fig.  16. 


Fig.  17. 


flanged  ring  connects  the  fire  box  with  a  large  flue  which  conducts 
the  hot  gases  away.  The  necessary  handholes,  gages,  safety  valves, 
etc.,  are  provided.  This  form  is  not  economical  but  is  used  on 
account  of  the  little  attention  required. 

More  economical  forms  of  the  small  upright  boiler  are  illus- 
trated in  Fig.  16  and  17.  The  boiler  shown  in  Fig.  16  is  a  com- 
mon form;  externally  it  is  like  the  boiler  represented  by  Fig.  15, 
but  within,  it  has  a  somewhat  different  construction.  It  resembles 


TYPES  OF  BOILERS  21 

a  multitubular  boiler  placed  on  end.  The  fire  box  is  made  of  an 
inner  cylinder  stayed  to  the  outer.  The  top  of  the  fire  box,  called 
the  lower  tube  sheet,  is  connected  to  the  upper  head  by  tubes, 
through  which  the  hot  gases  pass  to  the  smoke  pipe.  It  will  be 
readily  seen  from  Fig.  16,  that  the  upper  ends  of  the  tubes  are 
surrounded  with  steam  while  the  lower  portions  are  covered  with 
water.  As  steam  is  a  poor  conductor  of  heat,  the  ends  of  these 
tubes  are  liable  to  injury  from. overheating. 

In  the  class  of  boiler  shown  in  Fig.  17  the  upper  ends  of  the 
tubes  are  below  the  water  level,  thus  avoiding  the  weakness  des- 
cribed in  connection  with  Fig.  1C.  The  upper  tube  sheet  is  sub- 
merged and  is  flanged  and  riveted  to  the  frustum  of  the  cone 
wrhich  forms  the  smoke  box.  The  chief  defect  in  this  boiler  is 
that  the  lower  part  of  the  cone  is  often  placed  too  near  the  shell; 
this  is  done  to  admit  more  tubes.  This  construction  restricts  the 
space  so  much  that  there  is  not  sufficient  room  for  the  steam  to 
rise  as  it  is  formed  on  the  tubes.  The  cone,  which  is  subjected  to 
external  steam  pressure,  is  likely  to  be  weak  and  is  usually  care- 
fully stayed. 

These  small  upright  boilers  require  no  brick  setting,  as  the 
fire  box  is  within  the  boiler  and  the  cast-iron  foundation  forms 
the  ashpit. 

MANNING  BOILER. 
Vertical— Many  Small  Fire  Tubes— Fire  Box. 

The  Manning  boiler  is  illustrated  in  Fig.  18.  In  order  to 
get  a  large  heating  surface,  it  is  made  20  to  30  feet  high.  It  is, 
in  general,  similar  to  the  upright  boiler  shown  in  Fig.  1C.  At 
the  lower  portion,  the  shell  is  of  greater  diameter  than  at  the  top 
in  order  to  provide  a  large  grate  area.  The  inner  fire  box  is 
stayed  to  the  shell  by  screw  stay  bolts.  .  As  the  fire  box  is  sur- 
rounded by  water  and  there  are  many  long  tubes  there  is  a  large 
heating  surface.  The  tubes  are  arranged  in  concentric,  circles  with 
a  space  for  circulation  in  the  middle. 

The  external  fire  box  is  joined  to  the  shell  by  a  double  flanged 
ring  as  shown  in  Fig.  19;  or,  by  the  cone-shaped  section  as  illus- 
trated in  Fig.  20.  The  top  edge  of  the  internal  fire  box  is  riveted 
to  the  lower  tube  sheet  which  is  flanged.  The  bottom  of  the  inner 
fire  box  is  connected  to  the  outer  shell  by  a  welded  ring  (shown 


87 


22 


TYPES  OP  BOILERS 


00000  0000     O     O 
0000  0  0   O   O    O     O 
1 000  00  0    0    O 
0  0  0   0    O 
000  0  0  0   0 

0000 


Fig.  18. 


in  section  in  Figs.  19  and 
20)  called  the  foundation 
ring.  The  water  space  be- 
tween the  inner  and  outer 
fire  box  plates,  called  the 
water  leg,  should  be  large. 

This  boiler  is  cleaned  by 
means  of  handholes.  They 
are  placed  in  the  shell  plates 
near  the  lower  tube  sheet,  in 
the  external  fire  box  just  over 
the  furnace  door,  and  at  the 
bottom  near  the  foundation 
ring.  As  there  are  no  man- 
holes for  cleaning,  the  boiler 
is  suited  to  good  feed  water 
only. 

The  feed  pipe  enters  the 
shell  at  the  side  near  the 
middle  of  the  water  space, 
and  extends  across  the  boiler; 
it  is  perforated  to  distribute 
the  water. 

The  heating  surface  con- 
sists of  the  inside  of  the  fire 
box  and  the  tubes  up  to  the 
water  level,  and  the  tube 
sheet.  That  part  of  the  tubes 
above  the  water  line  is  the 
superheating  surface;  that  is, 
the  heat  from  the  gases  passes 
through  the  metal  of  the 
tubes  to  the  steam,  thus  rais- 
ing its  temperature  without 
raising  its  pressure.  Steam 
heated  under  these  condi- 
tions is  called  superheated 
steam.  In  small  vertical 


TYPES  OF  BOILERS 


23 


boilers  this  superheating  surface  is  not  desirable  because  the  work 
of  the  small  boiler  does  not  require  superheated  steam  and  the 
tubes  are  likely  to  be  burned  by  the  intense  heat.  "With  the  long 


o  o  o  o  o  o  o  o 
oooooo  oo 
ooooo  o  o  o 
ooooo  oo  o 
ooooo  o 

0    O     O 


0    0    O    O 

oooooo  o 

0000000 

oooooo  o 

00  0  0    0    0    O 


Fig.  19. 


Fig,  20. 


tubes  of  the  Manning,  the  gases  are  not  as  hot  when  they  reach 
the  top,  and  as  this  boiler  is  built  in  large  powers  (200  horse-power 
being  common)  the  engines  supplied  are  built  for  economy  and 
require  dry  if  not  superheated  steam. 

RETURN-TUBE  BOILERS. 
Horizontal  -Many  Small  Fire  Tubes— Internally-Fired. 

The  boilers  hitherto  described  are  used  mainly  for  stationary 
work,  the  exceptions  being  so  few  that  they  need  not  be  even  men- 
tioned. Let  us  now  discuss  another  modification  of  the  fire-tube 


89 


TYPES  OF  BOILERS 


boiler — one  that  has  been  and  is  now  extensively  used  in  marine 
work.  The  parts  of  the  return -tube  boiler  are  essentially  the  same 
as  those  of  flue  boilers  (Cornish  and  Lancashire)  and  the  multi- 
. tubular  boiler.  They  are,  however,  arranged  differently  in  order 
to  be  used  on  board  ship. 

The  earliest  forms  of  marine  boilers,  working  with  pressures 
of  15  to  30  pounds  per  square  inch,  were  square  or  box-shaped. 
They  were  economical  and  of  convenient  form  for  ships.  When 
higher  steam  pressures  became  necessary,  the  flat  surfaces  required 
so  much  staying  that  they  were  abandoned  and  the  cylindrical 
type  introduced,  as  this  form  is  the  best  of  the  practical  shapes  to 
resist  internal  pressure.  The  cylindrical  form  may  not  be  as  con- 
veniently stowed  aboard  ship,  but  it  will  stand  much  higher  pres- 


Fig.  21. 


sures.  The  cylindrical  marine  boiler  is  frequently  built  for  170 
pounds  per  square  inch. 

The  single=ended,  return-tube  boiler,  shown  in  Fig.  21,  com- 
bines the  internal  furnace  flue  of  the  Cornish  type  and  the  numer- 
ous small  fire  tubes  of  the  multitubular.  The  cylindrical  shell  is 
made  up  of  plates  riveted  together  and  to  the  flat  ends  of  the 
boiler,  which  are  flanged  to  fit  the  shell. 

The  furnace  is  cylindrical,  three  to  four  feet  in  diameter  and 
about  seven  feet  in  length.  The  front  end  of  the  furnace  flue  is 
riveted  to  the  front  end  plate,  which  is  flanged  for  the  purpose. 
The  back  end  is  riveted  to  the  combustion  chamber  plates.  For- 


TYPES  OF  BOILERS 


merly,  the  flue  was  a  plain  cylinder,  but  as  a  plain  cylinder,  unless 
of  small  diameter,  cannot  stand  much  external  pressure,  it  soon 
became  necessary  to  strengthen  it.  This  was  done  by  means  of  the 
curved  ring  shown  in  Fig.  5  and  other  methods;  but  at  present 
the  corrugated  flue  is  used,  one  form  being  shown  in  Fig.  6. 

The  grate  is  placed  at  about  the  center  of  the  height  of  the 
furnace  flue;  the  space  above  this  grate  is  occupied  by  the  fire  and 
hot  gases,  below  it  is  the  ashpit.  As  will  be  seen  from  the  arrows 


Fig.  22. 

in  Fjg   21,  the  hot  gases  fill  the  space  above  the  fire,  the  combus- 
tion chamber,  the  tubes  and  the  uptake. 

The  combustion  chamber  in  which  the  products  of  combus- 
tion are  completely  burned,  is  formed  of  flat  and  curved  plates 
flanged  at  the  edges  and  riveted  together.  The  shape  of  the  plates 
is  shown  in  Fig.  21,  which  is  a  sectional  view  of  a  single-ended 
marine  boiler.  The  back  tube  sheet  forms  the  front  of  the  com- 
bustion chamber.  The  space  aroynd  the  tubes,  furnace  flne,  and 
combustion  chamber  is  filled  with  wrater,  the  water  level  being  six 
to  eight  inches  above  the  top  rowT  of  tubes.  The  space  above  the 
water  level  is  called  the  steam  space. 


91 


TYPES  OF  BOILEftS 


As  the  return-tube  boiler  has  several  flat  surfaces,  this  type 
requires  careful  staying.  The  flat  ends  above  the  water  level  are 
prevented  from  bulging  by  long  stay  rods  which  are  similar  to 
those  in  the  multitubular  type.  Below  the  water  level,  the  furnace 
flue  and  the  tubes  aid  in  holding  the  flat  plates  together.  In  addi- 
tion, a  few  of  the  tubes  (shown  by  the  heavier  circles  in  Fig.  21) 
are  made  thicker  so  that  a  thread  may  be  cut  on  the  ends  which 
are  screwed  into  the  tube  sheets  and  held  by  thin  nuts.  The  com- 
bustion chamber  plates  are  stayed  to  the  rear  end  plate  and  the 
shell  by  short  screw  stay  bolts.  The  flat  top  of  the  combustion 
chamber  is  supported  by  girders  or  crown  bars. 

Number  of  Furnaces.  The  boiler  shown  in  Fig.  21  has  only 
one  furnace,  but  return-tube  boilers  frequently  have  two,  three,  or 
foiir  furnaces. 


Fig.  23. 

Fig.  22  shows  a  boiler  with  three  furnaces.  Large  furnaces 
are  more  efficient  than  small  ones  because  the  grate  area  increases 
directly  as  the  diameter,  while  the  air  space  above  the  grate  in- 
creases as  the  square  of  the  diameter.  The  greater  space  aids 
combustion.  The  length  of  the  grate  bars  is  nearly  constant  for 
all  sizes  of  flue  because  it  is  limited  by  the  distance  a  fireman  can 
throw  coal.  Furnace  flues  are  usually  from  36  to  54  inches  in 
diameter.  As  the  size  of  furnaces  is  fixed,  the  number  depends 
upon  the  size  of  the  boiler,  for  a  large  boilqr  must  have  a  large 
grate  area  which  can  be  obtained  only  by  using  several  furnaces. 
The  various  arrangements  are  shown  diagrammatically  in  Fig.  23. 

A  single-furnace  boiler  has  but  one  combustion  chamber.  A 
two-furnace  boiler  may  have  a  combustion  chamber  for  each  fur- 
nace or  it  may  have  a  common  combustion  chamber.  If  there  is 
but  one  boiler  on  board,  it  is  better  to  have  twro  combustion  cham- 


92 


TYPES  OF  BOILERS 


bers,  so  that  in  case  a  tube  bursts,  the  boiler  will  not  be  disabled. 
If,  however,  there  are  several  boilers,  it  is  better  to  have  a  common 
combustion  chamber  for  the  two  furnaces,  because  the  alternate 
stoking  keeps  up  a  more  nearly  constant  pressure  of  steam  and 
there  is  less  smoke.  Three-furnace  boilers  usually  have  three 
combustion  chambers,  while  four-furnace  boilers  have  two.  In 
case  four  furnaces  are  used  with  three  combustion  chambers,  the 
two  center  furnaces  lead  to  a  common  combustion  chamber  and 
each  outside  furnace  has  one. 


Double  ended  Boilers.  This  form  of  marine  return-tube 
boiler  is  practically  the  same  as  two  single-ended  boilers  placed 
back  to  back,  but  with  the  rear  plates  removed.  The  weight  of 
the  rear  plates  is  saved  and  there  is  less  loss  from  radiation.  This 
makes  the  double-ended  boiler  lighter  and  cheaper  in  proportion 
to  the  heating  surface.  Double-ended  boilers  are  often  made  10 
feet  in  diameter  and  18  feet  long. 


Q3 


28 


TYPES  OF  BOILERS 


There  are  two  distinct  classes  of  double-ended  return-tube 
boiler— those  having  all  the  furnaces  open  into  one  combustion 
chamber  and  those  having  several  combustion  chambers.  The 
boiler  having  but  one  combustion  chamber  has  the  disadvantage 
that  if  one  fire  is  being  cleaned  the  whole  boiler  may  be  cooled  by 


the  inrush  of  cold  air.  It  is  better  to  have  a  combustion  chamber 
for  each  furnace  or  at  least  have  a  combustion  chamber  for  the  fur- 
naces of  each  end.  The  usual  method  of  dividing  up  the  combus- 
tion chambers  is  by  water  spaces  as  shown  in  Fig.  24,  which  is  the 
section  of  a  boiler  ha v ing  a  combustion  chamber  for  each  furnace. 


94 


TYPES  OF  BOILERS 


Internal  Furnace  Return-Tube  Boiler.  Although  the  return  - 
tube  boiler  is  commonly  used  in  marine  work,  this  type,  with 
some  changes  in  detail,  is  used  in  plants  ashore.  Fig.  25  shows 


Fig.  25. 

the  construction  and  arrangement  of  parts.     The  flue  is  larger  in 
proportion  to  the  diameter  than  is  the  case  with  the  marine  form; 
the    combustion    chamber  is 
partly  external  to  the  shell,  that 
is,  the  rear  tube  sheet  is  also  the 
rear  end  plate.     This  arrange- 
ment does  away  with  the  neces- 
sity of  staying  the  flat  plates 
of  the  combustion  chamber. 

Another  form  of  internal 
furnace,  return -tube  boiler  is 
showrn  in  Fig.  26.  This  boiler 
usually  has  two  flues  extending 
from  the  front  to  the  back  head. 
The  grate  is  placed  in  the  cor- 
rugated portion  while  conical 
water  tubes  support  the  flue 
back  of  a  bridge  wall.  The 
large  furnaces  and  the  space  around  the  conical  tubes  provide  a 
combustion  chamber  of  ample  size. 


05 


30 


TYPES  OF  BOILERS 


The  arrows  show  the  direction  of  the  hot  gases.  After  leav- 
ing the  internal  flue  they  enter  the  return  tubes  which  are  below 
the  furnace;  before  leaving  the  boiler,  they  pass  underneath  the 
shell.  By  this  arrangement  the  hottest  gases  are  near  the  water 
line  and  the  cooler  gases  in  contact  with  the  cold  water,  thus  there 
is  the  greatest  difference  in  temperature  at  all  times.  At  each 
change  in  the  direction  of  the  hot  gases,  there  is  an  opportunity 
for  dirt  and  ash  to  fall  by  gravity  so  that  the  tubes  may  remain 
clean  and  efficient. 


Fig.  26. 

With  the  exception  of  the  foundation  there  is  no  brickwork. 
The  shell  is  covered  with  a  non-conducting  material.  This  boiler, 
like  the  Galloway,  has  a  large  steam  and  wrater  space,  thus  insur- 
ing dry  steam  and  great  reserve  power. 

THROUQH=TUBE  BOILERS. 
Horizontal— Many  Small  Fire  Tubes— InternalIy=Fired. 

Vessels  of  slight  draft  require  a  boiler  of  small  diameter. 
This  is  especially  true  of  gunboats  as  it  is  desirable  to  have  the 
boilers  below  the  water  line.  As  there  is  not  room  for  the  return- 
tube  boiler,  the  through-tube,  shown  in  Fig.  27,  is  sometimes 
used.  This  boiler  is  made  up  of  the  same  parts  as  the  return 
tube,  the  chief  difference  being  that  of  arrangement.  The  rear 


96 


TYPES  OF  BOILERS 


plate  of  the  combustion  chamber  forms  one  tube  sheet  and  the  end 
plate  forms  the  other.  The  top  of  the  combustion  chamber  is 
stayed  to  the  shell  by  sling  stays  which  are  bars  having  forked  ends 
fastened  to  the  shell  and  to  the  combustion  chamber. 


fOOO  OOOOO 

o    o     o  oooo 

O      O       O  0000   00( 

o    o     o  o     o.  o    o 


The  fire  is  in  a  flue,  or  flues,  which  leads  to  the  combustion 
chamber.  The  hot  gases  pass  from  the  combustion  chamber 
through  the  tubes  to  the  uptake  at  the  back  end.  The  chief  ob- 
jection to  this  form  is  its  length,  for  the  heating  surface  is  small 
unless  the  boiler  is  made  very  long. 


97 


TYPES  OF  BOILERS 


FIRE=BOX  BOILERS. 

LOCOMOTIVE  TYPE. 

Horizontal— Many  Small  Fire  Tubes— Externally-Fired. 

Although  vertical  fire-tube  boilers  may  be  classed  as  fire-box 
boilers,  yet  the  name  fire-box  boiler  is  usually  applied  to  the  loco- 
motive  type  whether  used  with  a  locomotive  or  as  a  stationary  boiler. 

The  usual  form  of  horizontal  fire-box  boiler  consists  of  a  cyl- 
indrical shell,  or  barrel,  partly  filled  with  tubes,  and  a  rectangular 


fire  box.  The  shell  is  prolonged  beyond  the  rear  tube  sheet  to 
form  a  smoke  box.  The  front  ends  of  the  tubes  open  into  the  fire- 
box, while  the  rear  ends  open  into  the  smoke  box.  The  hot  gases 
from  the  fire  pass  through  the  tubes  to  the  smoke  box  and  from 
thence  to  the  stack  or  uptake.  For  locomotive  work,  there  are  a 
large  number  of  small  tubes  (usually  2-inch),  but  for  stationary 
work  the  tubes  are  larger  and  less  numerous.  The  reason  for  this 
difference  is  that  in  the  locomotive  boiler  a  greater  heating  surface 
is  necessary,  and  to  obtain  sufficient  draft  to  burn  the  large  amount 
of  coal  for  this  heating  surface,  the  exhaust  fcteam  is  turned  into 
the  smoke  box.  The  blast  of  steam  carries  the  heated  gases  up 
the  stack  and  a  fresh  supply  of  air  passes  through  the  grate. 

The  cylindrical  shell  h  joined  to  the  fire  box  by  riveting  to  a 
flanged  ring  or  to  a  cone-shaped  portion  as  in  the  vertical  boiler. 
The  fire  box  has  a  rectangular  cross -section  and  usually  a  flat  top. 


TYPES  OF  BOILERS 


33 


99 


TYPES  OF  BOILERS 


100 


TYPES  OF  BOILERS 


Like  the  vertical  boiler  there  is  an  inner  and  an  outer  fire  box,  the 
inner  having  the  same  shape  as  the  outer,  except  that  the  top  is 
flat.  The  external  fire  box  is  connected  to  the  inner  by  short 
screw  stays.  The  space  between  is  called  the  water  leg.  The  flat 
top  is  stayed  by  girders  or  crown  stays.  These  are  sometimes  at- 
tached to  the  shell  by  sling  stays.  The  lower  portions  of  the  tube 
sheets  are  held  in  place  by  the  tubes;  the  upper  portions  are  stayed 
by  diagonal  stays. 


Fig.  31. 

The  chief  differences  in  the  various  forms  of  locomotive  boilers 
are  the  shape  of  the  flre  box  and  the  location  of  the  grate.  Loco- 
motive boilers  are  either  straight  top  or  wagon  top.  The  wagon 
top  boiler,  see  Fig.  28,  has  a  cone-shaped  portion  by  means  of 
which  the  boiler  is  larger  at  the  fire-box  end.  This  construction 
is  to  give  a  greater  steam  space.  The  increase  in  size  of  boilers 
has  raised  the  top  so  high  above  the  rails  that  the  wagon  top  is 
not  now  used  extensively;  the  straight  top,  see  Fig.  29,  is  more 
common. 


101 


36 


TYPES  OF  BOILEKS 


Belpaire  Boiler.  The  shell  and  fire  tubes  of  this  type  of 
boiler  are  practically  the  same  as  in  any  other  fire-box  boiler,  the 
peculiarity  lies  in  the  fire  box.  The  inner  and  outer  fire-box  plates 
are  horizontal  at  the  top,  and  the  sides  of  the  outer  fire-box  are 
continued  so  that  the  space  above  the  crown  sheet  is  rectangular  in 
section.  The  advantage  of  this  construction  is  that  the  staybolts 
holding  the  crown  sheets  and  side  sheets  can  be  placed  at  right 
angles  to  the  sheets.  This  reduces  the  tendency  to  bending  when 
under  pressure. 


Fig.  32. 

Wootten  Boiler.  In  this  type  also,  the  fire  box  is  the  chief 
portion  to  be  considered.  The  size  of  the  locomotive  fire  box  is 
limited.  With  older  types  the  width  was  limited  to  less  than 
three  feet  and  the  length  to  less  than  seven  feet.  This  was  because 
of  the  frames  and  the  distance  between  the  axles.  By  placing  the 
fire  box  above  the  axles,  the  width  was  increased  by  an  amount 
equal  to  the  thickness  of  the  frames  or  about  seven  inches,  and  the 
length  increased  to  about  eleven  feet.  By  raising  the  fire  box  still 
more  and  placing  it  above  the  driving  wheels,  the  width  can  be 
still  further  increased. 

A  broad,  shallow  fire  box  is  required  if  anthracite  coal  is 
used.  The  Wootten  fire  box,  shown  in  Fig.  30  and  31,  is  very 
wide  and  is  placed  on  top  of  the  driving  wheels.  Formerly,  a  com- 
bustion chamber  was  placed  between  the  end  of  the  grate  and  the 
tubes,  but  as  it  was  found  to  be  unnecessary,  it  is  not  now  used. 


102 


TYPES  OF  BOILERS 


.'',7 


Lentz  Boiler.  The  object  of  the  design  shown  in  Fig.  32  is 
to  avoid  the  use  of  stays.  To  do  this  no  flat  plates  are  used,  ex. 
cept  the  tube  sheets  and  these  are  stayed  by  the  tubes.  The  fire- 
box is  in  the  form  of  a  corrugated  flue  similar  to  those  in  inter- 
nally-fired, return -tube  boilers.  As  this  is  circular  it  requires  no 
stays.  The  shell  is  circular  and  shaped  as  shown  in  the  illustra- 
tion. This  type  has  been  much  used  in  Europe,  but  a  few  have 
been  built  in  this  country. 

FIRE=BOX  BOILER  FOR  STATIONARY  WORK. 

The  fire-box  boiler,  usually  called  the  locomotive  boiler,  is 
often  used  for  stationary  work,  traction  engines,  and  for  vessels  of 
light  draft.  This  type  of  boiler,  slightly  modified,  is  sometimes 


Fig.  33. 

used  for  generating  the  steam  for  heating  buildings.  It  is  econom- 
ical and  durable  when  used  with  natural  draft.  The  chief  differ- 
ences in  construction  are  larger  tubes  because  of  the  draft,  and  the 
changes  due  to  method  of  support.  A  common  form  is  shown  in 
Fig.  33.  This  type  has  been  built  in  large  sizes  for  high  pressure, 
but  when  so  made  is  expensive. 


103 


TYPES  OF  BOILERS 


PECULIAR  FORflS. 

Fire=Tube  Boilers,  but  differing  from  those  described. 
Return  Tubular  as  Stationary.  Boilers  of  the  form  shown 
in  Fig.  34  resemble  the  locomotive,  fire-box  type,  but  in  addition 
have  return  tubes.  The  hot  gases  reach  the  uptake  by  means  of 
these  tubes  instead  of  passing  to  the  chimney  from  the  smoke-box 
end.  Thus  they  combine  the  advantages  of  the  fire-box  type  and 
the  return-tube  type  without  the  brick  furnace.  The  water  sur- 
rounds the  furnace  on  all  sides  except  the  front.  They  are  built 
in  sizes  from  12  to  70  horse-power.  As  Fig.  34  shows  the  con- 
struction so  clearly,  further  description  is  unnecessary. 


Fig.  34. 

The  Cochrane  Vertical  Boiler  is  somewhat  like  the  return- 
tube  "boiler  in  point  of  arrangement  of  heating  surface.  This 
boiler  is  shown  in  section  in  Fig.  35.  The  hot  gases  pass  from 
the  furnace  to  the  combustion  chamber,  then  through  the  tubes  to 
the  uptake.  The  heating  surface  consists  of  tubes  and  the  plates 
of  the  fire  box  which  is  surrounded  by  water  except  the  bottom. 
The  crown  of  the  boiler  and  of  the  fire  box,  being  hemispherical, 
require  no  staying.  The  hemispherical  crown  also  allows  a  large 
steam  space.  The  flat  plates  (the  tube  plates)  are  held  together 
by  the  tubes. 

The  Shapley  Boiler,  shown  in  Fig.  36,  may  be  called  a 
return -flue  vertical  boiler.  The  upper  portion  is  a  reservoir  for 


104 


TYPES  OF  BOILERS 


water  and  steam  and  the  lower  contains  the  fire  box.  The  crown 
sheet  of  the  fire  box  is  stayed  to  the  top  by  through  stays.  The 
hot  gases  from  the  fire  rise  in  the  fire  box,  pass  through  short 
horizontal  tubes  to  an  annular  space.  This  annular  space  is  con- 
nected to  the  flue  at  the  base  by  vertical  tubes  passing  through 
the  water  space. 


Pig.  35. 

This  boiler  has  a  large  combustion  chamber;  the  fire  box  is 
surrounded  by  water,  and  the  crown  sheet  and  tubes  are  removed 
from  the  intense  heat  of  the  fire.  This  arrangement  increases  the 
heating  surface,  allows  complete  combustion  and  results  in  a  du- 
rable boiler.  The  base  is  partially  filled  with  water  so  that  any 
sparks  carried  over  will  be  quenched. 

Robb=Mumford.  This  boiler  resembles  the  through- tube 
internally-fired  boiler  (see  Fig.  27)  in  that  the  fire  is  within  a  corru- 
gated flue  and  the  tubes  lead  from  this  flue  to  the  rear  of  the  boiler. 


105 


40 


TYPES  OF  BOILERS 


The  Kobb-Mnmford  boiler  consists  of  two  cylindrical  drums 
or  shells,  connected  at  each  end  by  a  neck.  See  Fig  37.  The 
upper  drum  is  a  steam  and  water  drum,  the  water  level  being  at 
about  the  middle.  The  lower  shell  is  larger  and  is  inclined  about 
one  inch  in  twelve  to  increase  the  circulation,  and  facilitate  wash- 
ing out.  In  this  lower  shell  is  the  corrugated  flue  containing  the 

•  grate.  The  fire  tubes 
nearly  fill  the  remaining 
portion  of  the  shell  as 
shown. 

The  furnace,  in  which 
the  coal  is  burned,  is 
surrounded  by  water;  the 
hot  gases  pass  through 
the  tubes  to  the  rear,  re- 
turn between  the  lower 
and  upper  shells  and  es- 
cape to  the  chimney  from 
the  front  of  the  boiler. 
The  steel  casing  keeps 
the  gases  in  contact  with 
the  drums.  The  water 
circulation  is  shown  by 
the  arrows.  The  mix- 
ture of  wrater  and  steam 
enters  the  upper  drum; 
the  steam  here  separates 
from  the  wrater  which 
flows  down  the  neck  at  the 
forward  end.  A  semi- 
circular baffle  plate  directs  this  water  around  the  furnace  to  the  bot- 
tom. The  feed  water  enters  at  the  rear  of  the  steam  and  water  drum. 
As  compared  with  the  multitubular  boiler  one  can  readily  see 
that  the  drums  can  be  made  much  thinner  on  account  of  the  small 
diameter.  The  tubes  are  short,  straight,  and  easily  cleaned.  The 
internal  furnace  does  away  with  much  of  the  loss  from  leakage. 
As  the  water  is  well  subdivided,  steam  can  be  raised  rapidly  and 
there  is  little  danger  of  a  disastrous  explosion. 


Fig.  3G. 


106 


TYPES  OF  BOILERS 


41 


Directurn.     The  Begg's  "  Directurn  "  boiler  (Fig.  38")  is,  in 

OO  \          c5  / 

brief,  a  horizontal,  externally-fired,  multitnbular  boiler  in  which 
tubes  conduct  hot  gases   through    the  space   behind  the   bridge. 


,This  boiler  consists  of  a  shell  partly  filled  with  3-inch  tubes.  The 
rear  of  the  furnace  is  a  throat  sheet  in  which  4-inch  tubes  are  ex- 
panded. The  other  ends  are  expanded  into  the  rear  end  plate  which 
is  made  large  enough  for  the  purpose. 


The  boiler  is  encased  in 


107 


12 


TYPES  OF  BOILERS 


steel  plates  lined  with  fire  brick  which  is  held  in  place  by  rods 
passing  through  the  notches  as  shown.  The  manhole  for  entering 
the  boiler  is  placed  in  the  front  head  instead  of  in  the  shell  as  is 
frequently  done. 


Fig.  38. 

WATER=TUBE    BOILERS. 

The  water-tube  boiler  differs  essentially  from  the  fire-tube. 
The  names  indicate  the  chief  point  of  difference.  In  the  fire-tube 
boiler,  the  tubes,  which  are  surrounded  with  water,  conduct  the 
hot  gases  to  the  smoke  box.  In  the  water-tube,  the  tubes  are  filled 
with  water,  and  the  hot  gases  pass  over  and  among  them  on  their 
way  to  the  chimney. 

Although  flue  boilers  and  the  tubular  types  were  introduced 
at  an  earlier  period  than  the  water-tube,  yet  the  last-named  type  is 
not  a  new  form  of  steam  generator.  About  a  century  ago,  John 
Stevens  invented  a  water-tube  boiler  and  fitted  it  to  a  steamboat. 


TYPES  OF  BOILERS 


This  boiler  (Fig.  89)  was  a  combination  of  small  tubes  connected, 
at  one  end  to  a  reservoir.  Thus  the  "  porcupine  "  was  one  of  the 
earliest  forms.  At  various  times  since  then,  many  ideas  have  been 
worked  out  both  for  marine  and  stationary  boilers.  During  the 
last  fifteen  years,  however,  the  water-tube  boiler  has  been  steadily 
growing  in  favor,  the  chief  reasons  being — the  necessity  of  higher 
steam  pressures,  greater  reliability  of  materials,  greater  skill  in 
design  and  workmanship,  and  more  intelligent  management. 

It  is  not  within  the  province  of  this  instruction  paper  to  dis- 
cuss the  relative  merits  of  fire-tube  and  water-tube  boilers,  but  a 
careful,  impartial  consideration  seems  to  show  that  as  far  as  econ- 


Fig.  39.    Stevens  Boiler. 

omy  of  running  is  concerned  there  is  but  little  difference.  The 
fire-tube  boiler  is  reliable  and  can  be  handled  by  those  possessing 
comparatively  little  knowledge  of  engineering.  Its  chief  defect 
seems  to  be  the  disastrous  results  following  an  explosion.  The 
water-tube  boiler,  on  the  other  hand,  is  safe,  and  suited  to  higher 
pressures,  but  requires  greater  care  in  management. 

Before  discussing  these  boilers  in  detail,  let  us  consider 
briefly  the  salient  points. 

Safety.  Probably  the  greatest  advantage  claimed  for  the 
water-tube  boiler  is  its  safety.  The  boiler  contains  much  less 
water  than  does  the  flue  or  tubular  boiler  and  the  water  is  divided 
into  small  masses,  thus  minimizing  serious  results  in  case  of  rup- 
ture. On  account  of  the  shape  and  arrangement  of  parts,  the 
circulation  is  usually  good,  and  no  part  exposed  to  the  fire  can  be 
uncovered  while  there  is  any  water  in  the  boiler.  The  tubes  can- 
not become  overheated  until  the  boiler  is  empty  and  with  an  empty 
boiler  there  cannot  be  a  serious  explosion. 


109 


TYPES  OF  BOILEKS 


Rapidity  in  Raising  Steam.  The  many  small  streams  into 
which  the  water  is  divided  as  it  passes  through  tire  furnace  greatly 
facilitate  the  absorption  of  heat.  Because  of  the  small  streams 
and  the  rapid  circulation,  the  water  is  converted  into  steam  in  a 
very  short  time.  Several  hours  (usually  five  to  seven)  are  re- 
quired to  raise  steam  to  working  pressure  in  a  tubular  boiler, 
while  in  many  water-tube  boilers,  steam  can  be  raised  to  over  200 
pounds  pressure  in  less  than  half  an  hour. 

Durability.  Most  water-tube  boilers  are  so  designed  that  no 
seams  are  exposed  to  the  fire  or  hot  gases.  The  seams  are  the 
weakest  part  of  a  boiler,  and  as  strains  due  to  unequal  expansion 
concentrate  at  such  points,  leaks  or  even  ruptures  are  liable  to 
occur.  In  the  water-tube  boiler,  the  joints  between  tubes  and 
tiibe  sheets  are  not  in  the  direct  path  of  the  hot  gases. 

Loss  of  Heat.  The  loss  of  heat  will  evidently  be  reduced  to 
a  minimum  if  the  heating  sur- 
faces are  such  thatfthe  heat  read- 
ily passes  through  to  the  water. 
The  small  diameter  of  the  water 
tubes  (2  to  4  inches)  allows  the 
use  of  thin  metal  which  does  not 
hinder  the  transmission  of  heat. 
The  rapid  circulation  in  the 
water-tube  boiler  prevents  the 
accumulation  of  sediment  which 
is  a  poor  conductor  of  heat. 

Still  further,  dust  and  dirt  does  not  readily  collect  on  the  convex 
surface  of  water  tubes,  but  the  inside  of  fire  tubes  soon  become 
choked  with  soot  unless  cleaned  frequently.  See  Fig.  40. 

Less  Weight.  It  is  a  well-known  fact  that  a  cylinder  of  large 
diameter  must  be  much  thicker  than  one  of  small  diameter  when 
the  internal  pressure  is  the  same.  The  thickness  of  the  shell  of  a 
fire-tube  stationary  boiler  is  not  excessive,  because  of  the  moderate 
diameter;  but  in  the  return-tube  marine  boiler,  the  shell  plates  for 
250  pounds  pressure  would  be  about  lj|  inches  thick.  The  diffi- 
culty of  working  such  thick  plates  and  their  great  weight  render 
the  cylindrical  boiler  unsuitable  for  high  pressures.  The  small 
tubes  and  drums  of  the  water-tube  boiler  may  be  made  quite  thin 


Fig.  40. 


110 


TYPES  OF  BOILEKS  45 

4 _^___^ 

even  for  very  high  pressures.  In  general,  it  may  be  said  that  for 
the  same  capacity  and  pressure,  the  weight  of  a  water-tube  boiler 
is  only  about  two-thirds  that  of  a  fire-tube. 

CLASSIFICATIONS. 

Many  attempts  have  been  made  to  classify  water- tube  boilers. 
By  some  writers  a  classification  based  on  circulation,  or  on  the 
principle  of  operation,  is  claimed  to  be  superior  to  any  division 
according  to  construction.  Therefore,  they  divide  them  into  classes 
as  follows — boilers  with  limited  circulation;  boilers  with  free  cir- 
culation; boilers  with  accelerated  circulation. 

In  the  first  part  of  this  Instruction  Paper,  is  given  a  classifica- 
tion according  to  features  of  construction.  No  classification  is 
altogether  satisfactory  because  boilers  overlap  into  other  divisions; 
a  water-tube  boiler  may  be  sectional,  of  the  double-tube  type,  have 
horizontal  tubes,  straight  tubes,  and  free  circulation.  In  order  to 
have  some  sort  of  classification,  and  as  no  discussion  will  be  entered 
into  regarding  relative  merits,  the  classification  given  on  page  6 
will  be  here  adopted  and  followed  as  closelyas  conditions  will  permit. 

Water-tube  boilers  are  divided  into  two  great  classes — hori- 
zontal and  vertical.  Under  these  heads  come  sectional  and  non- 
sectional,  straight-tube  and  curved-tube,  and  single-tube  and 
double-tube.  If  the  tubes  are  nearly  horizontal,  such  as  is  the 
case  of  the  Babcock  and  Wilcox,  Koot,  etc.,  the  boiler  will  be 
called  horizontal.  If  the  tubes  are  vertical,  or  nearly  so,  as  in  the 
Wickes,  Stirling,  etc.,  the  boiler  will  be  classed  as  vertical. 

Although  most  boilers  can  be  classified  as  outlined  on  page  H, 
there  are  a  few  of  such  peculiar  construction  and  arrangement  that 
they  must  be  placed  by  themselves  under  "•  Peculiar  Forms." 
These  are  described  without  any  further  attempt  at  classification. 

As  it  is  impossible  to  discuss  all  makes  of  boilers,  a  few  rep- 
resentative forms  will  be  considered  as  types  of  their  respective 
classes.  No  attempt  will  be  made  to  choose  any  make  as  being 
the  best,  because  many  conditions  must  be  considered  in  selecting 
a  boiler.  The  boilers  described,  except  in  a  few  cases,  are  now 
used  extensively  in  either  stationary  or  marine  wTork. 


Ill 


TYPES  OF  BOILERS 


TYPES  OF  BOILERS 


47 


HORIZONTAL  WATER-TUBE  BOILERS. 
BABCOCK  AND  WILCOX. 

Water  Tubes  Nearly  Horizontal— Steam  and  Water  Drum  Horizontal— 
Straight=Tube — Single=Tu  be— Sectional. 

Construction.  This  boiler  consists  of  a  large  number  of  lap- 
welded,  wrought-iron,  4-inch  tubes  connected  to  each  other  and  to 
a  horizontal  steam  and  water  drum.  The  arrangement  of  the  parts 
is  shown  in  Fig.  41  which  is  a  side 
view  of  a  much -used  form  of  this 
boiler.  Each  tube  is  expanded  into  a 
forging  of  the  form  shown  in  Fig.  42. 

The  tubes  in  a  vertical  row  enter 
one  piece  and  this  vertical  row  is  in- 
dependent of  the  others,  as  shown  in 
Fig.  43.  Thus  it  is  readily  seen  that 
this  is  a  sectional  boiler.  Fig.  43 
shows  also  the  "  staggered  "  arrange- 
ment of  the  tubes.  In  the  back  side 
of  the  front  header,  and  in  the  front 
side  of  the  rear  header,  holes  are 
drilled  into  which  are  expanded  the 
water  tubes.  In  the  front  side  of 
the  header  a  flanged  hole  opposite 
each  tube  is  fitted  with  a  hand-hole 
plate.  The  details  of  construction 
are  shown  in  Fig.  44.  The  tops  of 
the  headers  are  connected  to  the 

steam  and  water  drum  by  short  tubes  and  the  same  construction  is 
used  for  connecting  the  mud  drum  to  the  rear  header. 

Operation.  The  grate  is  at  the  front  end  of  the  boiler  under 
the  higher  end  of  the  tubes.  The  hot  gases  from  the  fire  are 
guided  by  division  plates  and  bridges,  so  that  after  rising  from  the 
grate  they  pass  between  the  tubes  to  the  combustion  chamber, 
which  is  under  the  steam  and  water  drum;  the  gases  then  pass 
downward  among  the  tubes,  and  after  rising  a  second  time  pass  off 
to  the  chimney.  In  this  way,  the  direction  of  the  currents  of  hot 
gases  is  at  all  times  almost  at  right  angles  to  the  tubes,  thus  im- 
pinging  upon  them  instead  of  passing  parallel  to  the  heating  sur- 


Fig.  42. 


Fig.  13. 


118 


TYPES  OF  BOILERS 


faces,  as  in  the  case  of  fire  tubes.     As  the  gases  impinge  three  times 
ao-ainst  the  staggered  tubes,  the  heating  surface  is  very  efficient. 

Circulation.  The  feed  water  enters  the  steam  and  water 
drum  through  the  pipe  shown  in  Fig.  44.  It  is  thus  heated  be- 
fore it  mixes  with  the  hot  water  in  the  boiler.  As  the  water  in 
the  tubes  becomes  heated,  it  rises  to  the  higher  end  where  it  i^. 


partly  converted  into  stealn;  a  column  of  water  and  steam  rises 
through  the  header  to  the  drum  in  which  the  steam  and  water 
become  separated.  The  cooler  water  at  the  rear  of  the  steam  and 
water  drum  flows  down  into  the  lower  end  of  the  tubes  and  as  it 
becomes  heated  rises.  Thus  there  is  a  continuous  circulation. 

Steam  is  taken   from  the  rear  end  of  the  steam  and  water 
drum.     The  solid  matter  in  the  water  is  not  deposited  on  the  tubes 


114 


TYPES  OF  BOILERS 


because  of  the  rapid  circulation;  it  falls  to  the  mud  drum  from 
which  it  is  blown  out. 

The  marine  form  of  this  boiler  has  a  cross  drum,  that  is,  the 
drum  is  at  right  angles  to  the  tubes  instead  of  parallel  to  them. 
It  is  similar  in  form  to  the  cross-drum  types  used  for  stationary 
work.  This  form  is  used  in  case  there  is  not  sufficient  head  room. 

ROOT. 

Water  Tubes  Nearly  Horizontal—Steam  and  Water  Drums  Horizontal 
— Straight=Tube— Single=Tube— Sectional. 

The  above  brief  outline  indicates  that  the  lioot  water-tube 
boiler  is,  in  its  main  features,  like. the  Babcock  and  Wilcox.  Lo 
fact  the  difference  is  in  detail 
of  construction  only.  Fig.  46 
shows  the  general  appearance 
when  a  part  of  the  brickwork 
is  removed.  It  will  be  seen  that 
there  is  a  large  steam  drum 
(cross  type)  at  the  top  in  addi- 
tion to  the  small  steam  and 
water  drum  over  each  section. 

Construction.  The  Eoot 
water- tube  boiler  is  composed 
of  4-inch  lap-welded  wrought- 
iron  tubes.  These  tubes  are 
expanded  into  cast  iron  headers 
as  shown  in  A,  Fig.  45.  A  ver- 
tical section  is  formed  by  plac- 
ing one  pair  upon  another  as 
shown  at  B,  Fig.  45.  One  tube 
of  each  pair  is  connected  to  one 
above  it  by  a  flexible  bend,  by 
means  of  which  is  obtained  an 
uninterrupted  circulation  from 
the  bottom  to  the  top  of  the  Fig.  45 

section.     A   metallic   packing 

ring  (see  C,  D,  and  E,  Fig.  45)  insures  a  tight  joint  between  the 
bend  and  the  header.     F,  Fig.  45,  shows  an  enlarged  end  of  a  bend. 


115 


50 


TYPES  OF  BOILEKS 


To  form  the  boiler  several  of  these  vertical  sections  are  placed 
side  by  side.  These  vertical  rows  are  not  rigidly  connected  because 
the  lower  tubes  being  nearer  the  fire  expand  more  than  those  above. 


GTi 


a 


Circulation.  Each  section  has  its  overhead  drum  into  which 
the  water  and  steam  is  discharged  from  the  tubes.  At  the  rear 
of  the  boiler  and  at  the  end  of  each  steam  and  water  drum,  a  ver. 


116 


TYPES  OF  BOILERS  51 

tical  pipe  leads  to  a  cross  drum  beneath;  this  drum  is  a  common 
reservoir  for  all  the  sections.  The  feed  water  enters  this  drum 
and  meets  the  hot  water  coming  from  above.  The  mixing  of  the 
water  results  in  a  temperature  which  prevents  any  trouble  from 
unequal  expansion.  The  cross  drum  (reservoir)  is  also  connected 
by  vertical  pipes  to  another  drum  which  is  below  and  parallel  to 
it;  this  is  the  mud  drum.  From  the  feed  reservoir,  the  mixture 
of  feed  and  circulating  water  descends  to  the  mud  drum  in  which 
the  solid  impurities  are  left.  The  circulating  water  then  flows 
from  the  top  of  the  mud  drum  into  the  lower  end  of  the  tubes. 
As  these  tubes  are  surrounded  by  hot  gases,  the  water  becomes 
heated  and  rises  through  the  tubes  to  the  steam  and  water  drums. 
This  heated  water  contains  bubbles  of  steam  which  leave  the  water 
and  collect  in  the  steam  drum.  The  water  flows  through  the  steam 
and  water  drum  and  descends  to  meet  the  entering  feed  water.  The 
water  level  is  at  about  the  middle  of  the  steam  and  water  drums. 

The  hot  gases  from  the  fire  pass  among  the  tubes  three  times  in 
practically  the  same  manner  as  in  the  Babcock  and  Wilcox  boiler. 

WORTHINQTON. 

Water  Tubes  Nearly   Horizontal— Steam  and  Water  Drum   Horizontal 
—Straight-Tube— Single-Tube— Sectional. 

Construction.  This  form  of  boiler  is  much  the  same  in  prin- 
ciple and  operation  as  the  Babcock  &  Wilcox  boiler,  but  the  parts 
are  differently  proportioned  and  arranged;  see  Fig.  47.  The  fur- 
nace extends  under  the  entire  boiler,  and  the  tubes  are  set  over  it 
close  together  in  oppositely  inclined  series.  No  flame  walls  or 
baffle  plates  are  used. 

Boilers  up  to  125  H.  P.  are  usually  made  to  fire  at  the  end  as 
shown  in  Fig.  47,  in  which  the  tubes  extend  across  the  furnace 
viewed  from  the  front,  and  the  steam  and  water  drum  is  at  right 
angles  to  the  tubes.  In  the  side-fired  boilers  the  tubes  extend 
from  front  to  back,  and  the  steam  and  water  drum  from  side 
to  side;  this  arrangement  is  better  adapted  for  large  units  and  for 
setting  in  battery.  The  tubes  of  each  vertical  row  are  expanded 
into  straight  headers  which  contain  seven  or  eight  tubes.  See  Fig. 
48.  Opposite  each  tube  is  a  hand  hole.  These  headers  are  ar- 
ranged close  together,  forming  the  boiler  enclosure. 


117 


TYPES  OF  BOILERS 


53 


Circulation.  The  feed  water  enters  the  steam  and  water  drum 
and  the  circulation  carries  it  down  to  the  mud  drums  through 
large  circulating  tubes  which  are  outside  of  the  furnace.  See  Fig. 
48.  From  the  mud  drum  it  enters  the  lower  series  of  headers  and 
rises  through  the  inclined  tubes  over  the  fire  into  the  upper  headers. 


Fig.  48. 


Fig.  49. 


The  water  now  containing  bubbles  of  steam  enters  the  steam  and 
water  drum  by  means  of  short  tubes  shown  in  Figs.  47  and  48. 

The  covering  for  this  boiler  is  an  iron  casing,  no  brick  being 
used  except  to  enclose  or  line  the  furnace. 

HEINE. 

Water  Tubes  Nearly  Horizontal— Steam  and  Water  Drum  Parallel  to 
Tubes— Straight-Tube— Single-Tube— Non-Sectional. 

Construction.  The  Heine  water-tube  boiler  is  not  a  sectional 
boiler.  Instead  of  being  expanded  into  small  headers  grouped  to 
form  a  boiler,  all  the  tubes  are  expanded  into  the  inside  plates  of 


119 


TYPES  OF  BOILERS 


120 


TYPES  OF  BOILERS 


r,r> 


a  water  leg  at  each  end.  The  construction  of  this  water  leg  is 
shown  in  Fig.  50.  It  is  composed  of  two  parallel  plates  flanged 
and  riveted  to  a  butt  strap.  The  plates  are  strengthened  by  short 
hollow  screw  stays  similar  to  those  used  in  the  water-leg  construc- 
tion of  fire-box  boilers.  At  the  top,  the  water  leg  is  curved  and 
joined  to  the  steam  and  water  drum  by  riveting.  Opposite  each 
tube  is  a  hand  hole  for  cleaning  or  replacing  a  defective  tube. 

Circulation.  The  feed  water  enters  at  the  front  of  the  steam 
and  water  drum  and  flows  into  the  mud  drum  D,  from  which  it 
passes  to  the  rear  header  with  much  less  velocity.  The  water  is 
warmed  while  passing  through  the  pipe  leading  to  the  mud  drum, 
and  as  it  flows  slowly  through 
the  mud  drum  it  deposits  its 
sediment.  The  accumulated 
sediment  is  blown  off  by 
means  of  the  blow-off  pipe 
N.  The  water,  as  it  becomes 
heated  in  the  mud  drum, 
rises  and  passes  to  the  front 
of  the  mud  drum,  from  which 
it  flows  in  a  thin  sheet  .to 
the  rear  of  the  steam  and 
water  drum  and  to  the  rear 
water  leg.  From  the  rear  Fig.  50. 

water  leg,  it  enters  the  tubes 

in  which  it  is  partially  converted  into  steam.  The  mixture  of 
steam  and  water  enters  the  higher  end  of  the  drum  from  the 
water  leg,  and  as  there  is  but  a  thin  layer  of  water  in  the  steam  and 
water  drum,  the  steam  readily  rises  through  it.  A  deflection  plate 
prevents  water  from  being  carried  to  the  perforated  steam  pipe  A. 

The  flow  of  hot  gases  from  the  fire  is  directed  by  light  tile 
placed  on  the  upper  and  lower  rows  of  tubes  as  shown  in  Fig.  51. 
The  hot  gases  flow  nearly  parallel  with  the  tubes  instead  of  across 
*Jiern  as  in  the  Babcock  and  Wilcox. 
ATLAS. 

Water   Tubes    Nearly    Horizontal— Steam    and    Water    Drums  (Cross 
Type)   Horizontal— Straight-Tube— Single=Tube— Non-Sectional. 

This  make  of  water-tube  boiler  does  not  need  a  full  descrip- 
tion as  Figs.  52  and  53  show  both  the  general  arrangement  of 


121 


r,6 


TYPES  OF  BOILERS 


122 


II 


TYPES  OP  BOILERS 


parts  and  the  details  of  water-leg  construction.  The  general  de- 
scription of  the  Heine  boiler  is  applicable  to  this  type.  A  few 
points  of  difference,  however,  should  be  pointed  out. 

There  are  three  drums  running  crosswise  the  tubes.  The 
front  and  rear  drums  are  made  of  the  same  plates  as  the  water 
legs.  This  is  shown  in  the  illustrations.  The  reasons  for  this 
method  of  construction  are  that  it  gives  a  "  throat "  area  of  about 
80  per  cent  of  the  area  of  the  leg  and  prevents  all  seams  from 
coming  in  contact  with  the  furnace  gases.  The  two  drums  are 
connected  on  the  water 
line  by  equalizing  tubes. 
In  the  rear  drum,  a  water 
purifier  receives  the  feed 
water  which  passes  down 
the  rear  leg,  then  through 
the  tubes  to  the  front  leg. 
In  the  last  portion  of  the 
tubes,  much  of  the  water  is 
converted  into  steam  which 
flows  through  the  front 
drum  and  the  superheating 
tubes  to  the  small  upper 
drum.  The  water  flows 
through  the  equalizing 
tubes  to  the  rear  drum  and 
joins  the  current  of  feed 
water. 

rr,i  Fig.    53. 

Ihe  front  drum   is 

made  36  inches  in  diameter,  the  middle  drum  24  inches,  and  the 
rear  drum  42  inches.  The  tubes  are  4  inches  in  diameter  and  the 
longest  are  18  feet  in  length. 

riOSHER. 

Water  Tubes  Nearly  Horizontal— Steam  and  Water  Drums  (Cross 
Types)  Horizontal— Curved-Tube— Single=Tube— Non-Sectional. 

The  chief  differences  in  appearance  between  this  boiler  and 
those  already  described  are  shorter  tubes,  making  a  more  compact 
boiler,  and  the  curved  tubes.  This  type  is  more  often  used  in 


123 


58 


TYPES  OF  BOILERS 


124 


TYPES  OP  BOILERS 


r,9 


marine  than  in  stationary  work.  The  boiler  consists  of  a  large 
steam  and  water  drum  connected  to  a  smaller  water  drum  by 
slightly  curved  tubes.  The  steam  drum  is  supported  by  two  large 
circulating  pipes  (one  at  each  end)  which  are  connected  by  other 
pipes  to  the  water  drum.  Thus  the  circulation  is  down  these  pipes 


Fig.  55. 

and  along  the  pipe  at  the  bottom  (see  Fig.  55),  up  to  the  water 
drum  and  from  thence  to  the  steam  drum  by  the  tubes  which  are 
in  contact  with  the  hot  gases. 

The  feed-water  heater,  shown  in  Fig.  54,  consists  of  two 
small  drums  connected  by  tubes.  The  parallel  dotted  lines  in  the 
steam  drum  of  Fig.  54  show  how 

O 

tubes  are  removed  and  replaced. 

Fig.  55  shows  the  row  of  plugs  for 

this  purpose.     These  plugs  are 

illustrated  in  Fig.  56.     Each  plug 

is  a  conical-headed  bolt,  having  a 

short  piece  of  copper  tube,  a  pig.  56. 

washer,  and  a  nut.     The   conical 

head  and  the  copper  tube  are  inserted  in  the  hole  until  the  washer 

is  in  contact  with  the  outer  surface  of  the  drum.     The  nut  is  then 

screwed  up,  thereby  flaring  the  end  of  the  copper  tubing  as  shown. 


125 


TYPES  OF  BOILEKS 


Fig.  57. 


126 


TYPES  OF  BOILEKS 


61 


The  steam  pressure  on  the  conical  head  increases  the  tightness  of 
the  joint. 

.      THORNYCROFT-flARSHALL. 

Water  Tubes  Nearly  Horizontal— Steam  and  Water  Drum   (Cross 
Type)  Horizontal— Curved=Tube—Single=Tube— Non-Sectional. 

The  Thornycroft- Marshall  non-sectional  boiler  consists  of  a 
large  horizontal  steam  and  water  drum,  a  vertical  water  box  or 
header,  and  the  generating  tubes.  Like  the  Mosher,  the  tubes  are 
curved  slightly,  but  the  header  is  a  distinct  difference. 

The  general  features  of  construction  are  shown  in  Fig.  57. 
The  steam  and  water  drum,  sometimes  called  the  separator  barrel, 
is  simply  a  cylinder  with 

dished  ends.   The  water  level  /  .     , 

is  about  one-third  the  diam- 
eter of  the  cylinder.  The 
tubes,  which  are  3^  inches  in 
diameter,  are  connected  in 
pairs  to  a  junction  box  at 
one  end  and  to  a  water  box 
or  header  at  the  other  end. 
Thus  each  pair  forms  a  unit, 
but  the  two  tubes  of  the  unit 
are  not  in  the  same  vertical 
plane.  The  upper  tube  en- 
ters the  header  as  high  as  p;g  ^ 
possible  and  the  lower  ones 

enter  low  down,  thus  giving  considerable  upward  slope.  From 
near  the  top  of  the  water  box,  three  rows  of  tubes  lead  to  the  sep- 
arator barrel  as  shown  in  Fig.  58.  The  water  box  is  very  simple, 
the  flat  plates  are  stayed  by  short  hollow  screw  stay-bolts.  The 
junction  boxes  are  not  restrained  in  any  way;  this  construction, 
combined  with  the  slight  curve  of  the  tubes,  allows  free  expan- 
sion. The  slight  curve  also  allows  the  tubes  to  enter  the  separator 
barrel  and  the  water  box  at  right  angles  so  that  they  may  be 
expanded  in  place. 

Circulation.  The  feed  water  enters  the  steam  and  water  drum 
and  then  passes  to  the  water  box  through  the  two  lower  sets  of  tubes. 
See  Fig.  58.  The  water  enters  the  lower  ends  of  the  various  pairs 


127 


TYPES  OF  BOILERS 


Fig.  59. 


125 


TYPES  OF  BOILERS 


of  tubes,  as  shown  in  Fig.  58,  and  rises  in  the  tubes  while  in  con. 
tact  with  the  hot  gases  from  the  furnace.  The  mixture  of  steam 
and  hot  water  then  enters  the  header  from  which  it  passes  to  the 
steam  and  water  drum  by  means  of  the  highest  row  of  tubes.  The 
difference  in  height  of  the  two  tubes  of  a  unit  insures  good  circu- 
lation. A  baffle  plate  prevents  the  water  from  splashing  to  the 
steam  pipe. 

The  hot  gases  pass  upward  among  the  tubes  which  cross  £o 
frequently  that  they  take  almost  all  the  heat  from  them. 

NICLAUSSE. 

Water  Tubes   Nearly  Horizontal    Steam   Drum  Horizontal— Straight- 
Tube— Double-Tube— Sectional. 

This  boiler  differs  essentially  from  those  already  described  in 
that  it  is  of  the  double-tube  type.  In  general,  it  consists  of  a 
number  of  elements  which  form  a  vertical  header,  to  which  tubes 
are  connected.  The  tubes  are  set  at  an  angle  of  about  6  degrees 
to  the  horizontal.  Above  the  elements  is  a  transverse  steam  and 
water  drum  which  is  in  communication  with  the  headers.  The 
general  arrangement  of  parts  is  shown  in  Fig.  59. 

Construction.     The  interesting  features  of  this  type  of  boiler 


Fig.  60. 

are  the  design  and  construction  of  the  tubes  and  headers.  To 
increase  the  circulation  the  principle  of  the  "Field"  tube  is  em- 
ployed. In  this  construction,  the  outer,  or  generating,  tubes  (3| 
inches  in  diameter)  are  closed  at  one  end.  Each  generating  tube 
contains  an  inner  circulating  tube  which  is  l^J-  inches  in  diameter. 


129 


64 


TYPES  OF  BOILERS 


This  tube  is  open  at  both  ends.  The  closed  ends  of  the  generating 
tubes  are  supported  by  resting  in  holes  in  a  plate  or  rack  at  the  rear 
of  the  boiler.  The  forward  end  of  the  circulating  tube  is  attached 
to  a  cap  which  screws  into  the  outer  end  of  the  generating  tube.  A 
recess  in  this  cap  provides  a  bearing  for  an  arch  bar  which  spans  two 
tubes,  keeps  them  in  place,  and  is  itself  secured  by  a  nut  on  a  bolt 
which  is  screwed  into  the  header.  See  Fig.  60. 

The  front  end  of  the  generating 
tubes  is  of  peculiar  shape.  To 
allow  the  wrater  to  enter  the  circu- 

_T  TI      1J  lating   tubes,   and    to    fasten  the 

I  J£^®»  — «t— ~  4-otf  tubes  to   the  header  without  ex- 

panding  them,    each    generating 
tube  is  provided  at  the  open  end 

rfj     __||L=JLL~ :.T=        yrrX--U|\-       with  two  cone-shaped  portions; 
I         il     i£^»       (iflto'i  these  are  about  eight  inches  apart. 

The  first  cone  fits  into  a  taper 
hole  flanged  outward  in  the  front 
face  of  the  header,  and  the  sec- 
ond cone  fits  a  similar  hole  in  the 
rear  face  of  the  header.  Both  the 
rf.  n  -^Y  \  ^  holes  and  tubes  are  ground  to 

t  1        1  "          /<r^4#~"      ^e  same  S'IZG  anc*  taper.    .About 

j<        «  "^CJ^pk          niidway    between    the    cones,    a 

third  expanded  portion  occupies 
f      '  ?^  "  the  tube  hole  in   the  diaphragm 

f |. -.«  4— «••         /^CrT"Jy          or  middle  plate  of  the  header.    See 

I         i       IT  Fig.  60.     The  portion  of  the  tube 

within  the  header  is  called  the 
"lantern".  At  this  point  the 
tube  is  cut  away  so  that  water  may 
freely  enter  the  tube,  the  openings 
being  above  and  below.  In  Fig.  60,  the  upper  tube  is  in  its  nor- 
mal position,  but  the  lower  tube  has  been  turned  through  90 


Fig.  61. 


degrees  to  show  the  construction. 

To  stand  high  steam  pressures,  the  elements  of  the  headers 
are  made  of  wrought  steel  and  are  sinuous  in  shape.  Fig.  61 
shows  the  shape  of  the  header  and  the  positions  of  the  tubes. 


130 


TYPES  OF  BOILEKS 


65 


Fig.  62. 


131 


66  TYPES  OF  BOILERS 

Each  element  contains  24  tubes  in  two  vertical  rows  of  12  each 
In  the  middle  of  the  headers,  there  is  a  diaphragm  for  dividing 
the  interior.  The  front  passage  serves  as  a  "downcomer"  for  the 
water,  and  the  rear  is  the  "  upcomer  ",  or  riser,  for  the  mixture  of 
steam  and  water. 

The  lower  ends  of  the  headers  are  closed,  and  the  upper  ends 
flanged  to  connect  with  the  steam  and  water  drum,  which  is  42 

n 
inches  in  diameter. 

Circulation.  Fig.  60  gives  an  idea  of  the  direction  of  cir- 
culation. "Water  from  the  drum  descends  in  the  front  compart- 
ment of  the  header,  flows  into  the  circulating  tubes,  which 
communicate  with  the  front  compartment  only,  and  after  flowing 
the  length  of  the  circulating  tubes,  enters  the  generating  tubes. 
The  water  then  comes  back  through  the  annular  spaces  in  the  gen- 
erating tubes  to  the  rear  compartment  of  the  header,  because  the 
generating  tubes  communicate  with  the  rear  compartment  only; 
while  in  the  annular  space  it  is  partially  evaporated.  The  mixture 
of  steam  and  water  then  rises  to  the  drum. 

VERTICAL  WATER-TUBE  BOILERS. 

WICKES. 
Water  Tubes  Vertical— Straight=Tube— Single-Tube— Non-Sectional. 

Let  us  now  consider  a  water-tube  boiler  having  vertical  tubes. 
Fig.  62  shows  the  general  arrangement  of  the  parts  of  the  Wickes 
vertical  water-tube  boiler.  At  the  top  is  a  cylindrical  steam  and 
water  drum  into  which  the  upper  ends  of  the  vertical  tubes  are 
expanded.  At  the  bottom  is  a  cylindrical  mud  drum  of  the  same 
diameter  as  the  upper  drum.  The  tubes  are  straight  and  plumb 
when  in  position;  they  are  arranged  in  parallel  rows  with  a  clear 
space  between  rows  to  admit  a  small  hoe  to  remove  any  soot  that 
may  accumulate  on  the  tube  sheet  of  the  mud  drum. 

The  tubes  are  divided  into  two  compartments  by  heavy  fire- 
brick tile.  The  tubes  in  the  section  next  the  furnace  are  called 
"risers";  those  in  the  rear  are  the  "  downcomers,"  because  the 
heated  water  rises  to  the  steam  drum  through  the  front  tubes,  and 
the  cooler  water  flows  down  those  in  the  rear.  The  feed  water  is 
introduced  into  the  upper  drum.  The  direction  of  flow  of  hot 


132 


TYPES  OF  BOILERS 


Fig.  63. 


133 


TYPES  OF  BOILERS 


134 


TYPES  OF  BOILERS  69 

gases  is  the  same  as  that  of  the  water.     A  baffle  plate  in  the  steam 

c?  .T 

and  water  drum  directs  the  water  to  the  downcomers. 

The  furnace  is  external  and  built  entirely  of  brick.  The  hot 
gases  from  the  fire  cdme  in  contact  with  the  tubes  without  passing 
through  a  combustion  chamber. 

CAHALL. 

Annular  Steam  and  Water  Drum— Water  Tubes  Vertical— Straight- 
Tube— Single-Tube— Non-Sectional. 

The  Cahall  vertical  water-tube  boiler  consists  of  an  annular 
steam  and  water  drum,  a  cylindrical  mud  drum,  and  4-inch  vertical 
tubes.  The  generating  tubes  connect  these  two  drums  and  are 
placed  within  the  brick  setting.  An  external  circulating  pipe  also 
connects  the  two  drums.  As  this  pipe  is  filled  with  comparatively 
cool  water  and  the  generating  tubes  with  a  mixture  of  hot  water 
and  steam,  the  circulation  is  positive  and  rapid.  The  feed  water 
enters  the  steam  and  water  drum,  flows  down  the  external  pipe  to 
the  mud  drum  and  then  rises  in  the  generating  tubes  to  the  steam 
and  water  drum. 

The  fire  is  in  a  brick  furnace  at  one  side  of  the  boiler  as 
shown  in  Fig.  63.  The  hot  gases  rise  among  the  tubes.  The  an- 
nular form  of  the  Bteam  drum  makes  the  central  space  conical;  in 
this  space  several  deflecting  plates,  or  baffles,  cause  the  hot  gases  to 
flow  out  among  the  tubes.  After  heating  the  water  in  the  tubes 
the  hot  gases  pass  through  the  opening  in  the  steam  and  water 
drum  coming  in  contact  with  the  metal  containing  the  steam 
This  thoroughly  dries  the  steam  and  in  many  cases  slightly  super 
heats  it. 

The  steam  drum  and  also  the  mud  drum  are  equipped  with 
swinging  manheads.  The  steam  drum  also  has  several  handholes 
for  use  in  removing  and  replacing  tubes. 

STIRLING. 

Water  Tubes  Nearly  Vertical— Steam  and  Water  Drums  Horizontal— 
Curved-Tubes— Single-Tube— Non-Sectional. 

The  Stirling  boiler,  shown  in  Fig.  64,  consists  of  three  cylin- 
drical steam  and  water  drums  at  the  top,  and  a  mud  drum  at  the 
bottom.  The  lower  drum  is  connected  to  the  upper  drums  by 


135 


70  TYPES  OF  BOILERS 

three  sets  of  tubes  which  are  curved  slightly  at  the  ends.  The 
curved  tubes  allow  for  expansion  and  make  it  possible  to  have  the 
tubes  enter  the  drums  radially. 

The  feed  water  enters  the  rear  steam  and  water  drum  and 
coming  in  contact  with  the  hot  gases  just  before  they  enter  the 
uptake,  becomes  gradually  warmed.  This  heating  causes  most  of 
the  sediment  to  fall  to  the  mud  drum  from  \vhich  it  may  be  blown 
out  at  intervals.  The  mud  drum  is  protected  from  the  intense 
heat  of  the  furnace  by  the  bridge  wall. 

Each  set  of  tubes  are  separated  from  the  others  by  partition 
walls  or  baffles  of  fire-brick  tile  so  that  the  gases  from  the  furnace 
pass  along  the  entire  length  among  the  first  set  of  tubes;  they  are 
then  guided  downward  among  the  second  set  and  after  rising  again 
among  the  tubes  of  the  third  set,  escape  to  the  chimney.  By  thus 
having  a  long  passage  a  large  proportion  of  the  heat  is  taken  from 
the  gases  before  they  go  to  the  chimney.  The  fire-brick  arch  just 
above  the  furnace  insures  an  even  distribution  of  the  gases  and 

O 

promotes  combustion;  the  arch  heats  the  entering  air  to  a  high 
temperature,  thus  reducing  the  liability  of  chilling  the  tubes  by  an 
inrush  of  cold  air. 

Steam  is  taken  from  the  middle  drum  which  is  set  a  little 
higher  than  the  others  in  order  to  obtain  more  steam  space  and 
drier  steam.  The  boiler  is  surrounded  on  the  rear  and  two  sides 
by  the  brick  setting;  the  front  is  of  cast  iron  or  of  pressed  steel. 
Numerous  openings  in  the  brickwrork  allow  entrance  for  cleaning. 

This  type  of  boiler  is  flexible  and  adapted  to  cramped  places 
as  it  can  be  made  broad  with  little  height  or  high  with  small  floor 
area.  All  parts  are  either  cylindrical  or  spherical  in  shape  and  of 
wrought  metal.  The  curved  tubes  reduce  the  strains  resulting 
from  unequal  expansion  and  contraction. 

MILNE. 

Water  Tubes   Vertical— Steam  and  Water  Drum  Horizontal— Curved- 
Tube— Single=Tube— Non-Sectional. 

This  boiler  (Fig.  65)  is  in  many  respects  similar  to  the  Stirling 
(Fig.  G4),  but  an  inspection  of  the  two  illustrations  will  show 
several  differences.  In  the  Milne  boiler  there  is  but  one  steam 
and  water  drum  and  the, tubes  are  vertical  with  a  slight  curve  at 


136 


TYPES  OF  BOILERS 


?i 


Fig.  65. 


137 


72 


TYPES  OF  BOILERS 


Fig.  66, 


138 


TYPES  OF  BOILERS 


the  ends.  The  hot  gases  are  guided  by  division  plates  or  tile  so 
that  they  traverse  65  feet  of  tube-heating  surface  before  they  enter 
the  flue.  The  tubes,  being  vertical,  do  not  become  covered  with 
fine  ash,  nor  do  they  become  clogged  with  sediment  and  scale. 

Circulation.  The  feed  water  enters  the  row  of  tubes  at  the 
extreme  left  and  flows  downward  to  the  mud  drum.  It  then  rises 
as  it  becomes  heated  in  the  hotest  generating  tubes  and  enters  the 
steam  drum  as  steam  and  water.  This  method  of  feeding  keeps 
the  cold  feed  water  out  of  the  steam  drum,  and  as  the  cold  tubes 
containing  the  feed  are  placed  in  the  path  of  the  escaping  gases, 
but  little  heat  escapes  to  the  chimney. 

PECULIAR  FORMS. 
HAZELTON  OR  PORCUPINE. 

Water  Tubes  Horizontal— Steam  and  Water  Drum  Vertical— 
Straight=Tube— Single-Tube. 

The  Hazelton  water-tube  boiler  differs  in  many  ways  from 
the  boilers  thus  far  described.  Like  most  water- tube  boilers  it 

consists  of  a  steam  and  water 
drum  and  water  tubes,  but 
the  central  standpipe  is  ver- 
tical and  the  short  horizon- 
tal tubes  radiate  from  the 
central  drum.  According  to 
our  classification  it  is  not  a 
vertical  water-tube  boiler  be- 
cause the  tubes  are  horizon- 
tal, also,  it  is  not  a  horizontal 
boiler  as  in  general  appear- 
ance it  is  vertical. 

The  grate  is  circular  and 
formed   around    the  central 

drum  which  rests  on  a  circular  cast-iron  foundation.  Above  the 
grate,  the  central  drum  forms  part  of  the  heating  surface  and  is  the 
steam  reservoir;  below  the  grate  it  is  the  mud  drum,  which  maybe 
entered  by  means  of  a  manhole  just  below  the  grate!  As  shown 
in  Fig.  66,  the  standpipe  above  the  fire  is  provided  with  radial 
tubes.  The  appearance  of  these  tubes  gives  the  name  "porcupine". 


Fig.  67. 


139 


TYPES  OF  BOILERS 


The  standpipe  is  about  three  feet  in  diameter  for  large 
boilers.  The  tubes  are  about  four  inches  in  diameter,  and  two 
and  one-half  feet  long,  the  number  varying  with  the  capacity  of 
the  boiler.  The  outer  ends  of  the  tubes  are  closed  and  hemis- 
pherical, and  the  inner  ends  expanded  into  the  standpipe.  These 
tubes  are  free  to  expand  and  contract  without  bringing  any  strain 
on  the  boiler. 

Steam  is  taken  from  the  top  of  the  central  drum.  To  get  dry 
steam,  small  pipes  are  inserted  as  shown  in  Fig.  67.  The  steam 
passes  up  into  the  small  tube  at  the  top  of  the  standpipe  and 
then  through  the  small  pipes  to  the  ends  of  the  generating  tubes. 
It  then  flows  back  through  the  generating  tubes  to  the  annular  space 
and  from  thence  to  the  steam  pipe.  The  feed  pipe  enters  the  mud 


Fig.  68. 

drum  and  extends  upward  nearly  to  the  water  line;  it  then  returns 

nearly  to  the  level  of  the   grate,  terminating  in  a  spraying  nozzle. 

This  type  of  boiler  may  be  enclosed   in   a   brick  setting  as 

shown  in  Fig.  00  or  by  a  sheet  steel  covering  lined  with  fire  brick. 

HARRISON. 
Sectional  -Hollow  Cast-iron  Spheres  Instead  of  Tubes. 

All  boilers  thus  far  described  have  employed  tubes  as  a  means 
of  dividing  the  water  into  small  masses  in  order  to  make  the  heat- 
ing surfaces  more  effective.  In  the  Harrison  Safety  Boiler  (Fig. 
69)  tubes  are  not  used;  instead,  the  water  is  contained  in  hollow 


140 


TYPES  OF  BOILERS 


75 


cast-iron  spheres,  called  units.  These  units,  see  Fig.  08,  are 
arranged  in  vertical  rows,  called  slabs,  which  are  suspended  side 
by  side,  about  one  inch  apart,  from  an  iron  framework.  The 
brickwork  setting  is  merely  a  covering  to  keep  the  hot  gases  in 
contact  with  the  units;  it  does  not  support  the  boiler,  and  can  be 
repaired  without  disturbing  the  units. 


Fig.  69. 

The  use  of  units  in  place  of  tubes  combines  great  strength 
and  a  large  heating  surface.  They  are  strong  because  small  and 
spherical  and  on  account  of  the  division  of  the  water  into  small 
masses,  the  heating  surface  is  effective.  The  units  are  held  to- 
gether by  long  bolts  wThich  pass  through  the  centers  as  shown  in 
Fig.  68.  The  machined  faces  make  a  steam-tight  joint  without 
packing.  This  boiler  requires  the  same  fittings  as  other  boilers. 

The  great  advantage  of  this  boiler  is  safety.  From  the  con- 
struction, it  is  apparent  that  rupture  cannot  extend  beyond  the 
unit;  thus  disastrous  explosions  cannot  occur.  They  are  claimed 
to  be  durable,  economical,  rapid  steamers,  and  easily  handled. 
The  capacity  can  be  increased  by  merely  adding  more  slabs. 


141 


MANHATTAN    74TH    ST.    POWER    STATION,    NEW    YORK. 

Showing  Carey's  Magnesia  Pipe  and  Boiler  Covering. 


BOILER  ACCESSORIES 

PART  I 


BOILER  SETTING 

The  setting  for  a  stationary  boiler  consists  of  the  foundation  and 
as  much  of  the  furnace  and  flues  as  is  external  to  the  boiler  shell.  Some 
internally-fired  boilers — the  "Lancashire,"  for  instance — have  flues  in 
the  brick  setting.  The  whole  furnace  and  sometimes  the  flues,  as  is 
the  case  with  the  plain  cylindrical  boiler,  are  in  the  setting.  Vertical 
boilers  have  simply  a  foundation;  and  locomotive  boilers  have  no 
setting,  since  they  are  supported  by  the  frames  of  the  engines.  Marine 
boilers  are  usually  placed  on  saddles,  which  are  built  into  the  framing 
of  the  vessel. 

In  setting  a  boiler,  there  are  three  principal  requisites  that  should 
be  kept  in  mind :  1.  A  stable  support  or  foundation  for  the  shell,  so 
arranged  as  to  allow  for  proper  expansion  of  the  boiler.  2.  Properly 
arranged  spaces  for  both  furnace  flues  and  ash-pit.  3.  A  covering 
which  will  prevent  loss  of  heat  by  radiation,  and  which  will  not  allow 
moisture  to  accumulate  in  contact  with  the  plates. 

There  are  two  principal  methods  for  support — by  brackets 
riveted  to  the  shell  plates,  and  by  suspension  from  overhead  girders 
by  means  of  hooks,  rings,  etc.  In  any  case  the  supports  should  be 
so  arranged  that  each  shall  bear  its  proper  proportion  of  the  load  and 
at  the  same  time  allow  for  expansion.  If  the  boiler  is  short,  brackets 
are  generally  used ;  while  for  long,  plain  cylindrical  boilers  the  girder 
method  is  the  more  common.  If  a  very  long,  cylindrical  boiler  is 
supported  only  at  each  end,  the  great  weight  between  the  t\vo  sup- 
ports is  likely  to  cause  bending  and  an  excessive  strain  on  the  middle 
plates,  tension  in  the  bottom  plates,  and  compression  in  the  top  plates. 

The  first  requisite  for  a  setting  is  a  good  foundation.  If  the 
ground  is  firm  and  favorable  to  a  solid  foundation,  the  excavation 
need  be  only  three  or  four  feet  below  the  level.  If  it  is  soft,  the  exca- 
vation should  be  deeper,  and  the  extra  depth  filled  in  with  broken 
stone  mixed  in  with  cement,  gravel,  etc. ;  or,  for  very  heavy  work, 


143 


BOILER  ACCESSORIES 


piles  may  be  driven.  The  first  course  of  the  foundation  should  be 
large  stones  laid  in  cement;  upon  this  stonework  the  walls  may  be 
built,  either  of  stone  or  brick,  to  within  about  six  inches  of  the  floor- 
level;  and  above  this,  brick  should  be  used. 

Sometimes  the  bed  is  made  of  concrete  about  two  feet  in  thick- 
ness. If  the  soil  is  very  firm,  a  foundation  of  large  stonework  about 
three  feet  wide  may  be  built  under  the  side,  middle,  and  end  walls  only. 

In  determining  the  area  of  the  bed,  the  weight  that  is  to  be  put 
on  each  square  foot  should  be  estimated  carefully.  With  ordinary 
condition  of  the  soil,  this  should  not  exceed  2,000  pounds.  For 
greater  weights,  special  construction  must  be  used. 

The  supporting  and  enclosing  walls  are  built  upon  the  foundation, 
with  the  outer  walls  at  the  sides  and  rear  double,  the  space  between, 
usually  about  two  inches,  being  an  air-space  insulation  to  prevent 
loss  of  heat.  Projecting  bricks,  which  extend  from  the  outer  until  they 
just  touch  the  inner  wall,  allow  for  expansion  without  decreasing  the 
strength  of  the  inner  wrall.  The  side  walls  are  strengthened  by  buck- 
stays  or  binders,  which  are  kept  in  place  by  long  bolts,  secured  by 
nuts  on  each  end.  Fig.  1  shows  a  boiler  in  the  brick  setting,  sup- 
ported by  brackets,  the  front  brackets  resting  on  iron  plates  which 
are  built  into  the  walls;  the  rear  brackets,  being  supported  by  rollers, 
are  free  to  move  as  the  shell  expands.  If  designed  for  anthracite 
coal,  the  distance  between  the  shell  and  the  grate-bars  is  about  two 
feet;  for  softer  coal,  this  distance  is  increased  a  few  inches. 

The  furnace  is  lined  with  firebrick,  both  front  and  sides;  and 
sometimes  portions  back  of  the  bridge,  as  well  as  the  bridge  itself, 
may  thus  be  protected.  The  space  between  the  bridge  and  the  shell 
is  from  6  to  8  inches,  which  brings  the  hot  gases  into  close  contact 
with  the  boiler  before  they  enter  the  combustion  chamber  beyond, 
the  rear  and  side  walls  being  built  a  little  higher  than  the  top  row  of 
tubes.  The  fire-line  must  not  be  carried  above  the  water-line;  if  it 
is,  the  intense  heat  is  likely  to  injure  the  shell-plates.  Never  expose 
any  part  of  the  boiler  not  covered  by  water  to  the  flames  from  the 
furnace.  The  side  walls  are  built  about  the  same  height  as  the  rear 
walls.  The  space  at  the  rear  is  bridged  over  and  stiffened  by  T-irons. 
In  order  to  increase  the  neating  surface,  trie  top  is  arched  so  that  the 
hot  gases  will  pass  over  the  steam  space  before  they  enter  the  chimney. 


144 


BOILER  ACCESSORIES 


145 


BOILER  ACCESSORIES 


The  smoke  box  projects  over  the  front  end  of  the  boiler  and  has 
a  rectangular  uptake. 

Fig.  3  shows  the  top  view  of  the  same  boiler. 

The  front  is  usually  of  cast  iron,  with  doors  for  firing  and  cleaning 
and  for  access  to  the  tubes.  Soot,  dirt,  etc.,  are  removed  through  the 
door  in  the  brickwork  at  the  rear. 

The  end  which  contains  the  handhole  should  be  set  about  one 


Fig.  2.    Front  Elevation  of  Boiler  in  Setting,  Showing  Binders  Bolted  in 
Place,  to  Strengthen  Side  Walls. 

inch  lower  than  the  other  end,  so  that  the  sediment  and  detached  scale 
will  tend  to  accumulate  there. 

Internally-fired  boilers  may  also  be  enclosed  in  brickwork.  The 
setting  is  a  support  and  covering,  forming  the  side  flues  but  not  the 
furnace.  Excess  of  brickwork  surface  in  contact  with  the  shell, 
should  be  avoided,  as  brickwork  collects  moisture,  which  causes 
external  corrosion. 


143 


BOILER  ACCESSORIES 


147 


6 


BOILER  ACCESSORIES 


Water-Tube  Boilers.     The  settings  for  water-tube  boilers  are 
similar  to  the  settings  of  cylindrical  tubular  boilers.     Marine  water- 


Fig.  4. 


Fig.  5. 


Types  of  Brackets  for  Supporting  Boilers. 

In  Fig.  4  the  rivets  are  all  above  the  flange;  in  Fig.  5  they  are  both  above 
and  below  the  flange. 

tube  boilers  are  enclosed  in  sheet-iron  casing,  which  is  lined  with  non- 
conducting material,  usually  asbestos  or  m  agnesia. 

Supports.  There  are,  as  already  intimated,  two  common  methods 
of  supporting  boilers — 1.  By  means  of  brackets;  2.  By  suspending 
jrom  icrought-iron  beams. 

If  the  boiler  is  about  15  feet  long,  it  is  customary  to  use  two 
brackets  on  each  side.  If  more  than  15  feet,  three  on  each  side  are 
used.  The  front  brackets  rest  on  the  brickwrork,  but  the  others  rest 
on  small  iron  rollers  to  allow  for  expansion.  Brackets  are  so  arranged 
that  the  plane  of  support  will  be  a  little  above  the  middle.  There  are 
several  forms  of  brackets.  The  form  shown  in  Fig.  4  is  usually  made 
of  cast  iron,  and  is  provided  with  rivets  above  the  flange  of  the  bracket. 

n"n 


Fig.  6.  Fig.  7. 

Two  Methods  of  Supporting  Boilers  by  Suspending  from  Overhead  Beams. 

It  is  better  to  have  the  rivets  both  above  and  below  the  flange,  as  shown 
in  Fig.  5. 


148 


BOILER  ACCESSORIES 


Fig.  6  shows  one  method  of  suspending  from  beams.  A  lug, 
made  of  wrought  iron,  is  riveted  to  the  plates  of  the  boiler.  A  bolt 
having  one  end  bent  like  a  hook,  holds  the  lug  from  the  beam.  In 
Fig.  7  the  lug  is  replaced  by  a  loop  of  wrought  iron.  Fig.  8  shows 
another  method  of  suspension,  the  connection  between  the  rod  and 
the  boiler-plates  being  short  pieces  of  boiler-plate  arranged  for  flexi- 
bility. 

When  the  boiler  is  of  small  diameter,  it  may  be  suspended  as 
shown  in  Fig.  9. 

FURNACES 

To  get  the  maximum  efficiency  from  any  boiler,  it  is  necessary 
that  the  fuel  shall  be  properly  consumed,  and  that  the  proportions 


o  o 
o  o 
o  o 


Fig.  8.    Flexible  Support  for  Suspended  Boiler.    Fig.  9.    Illustrating  Method  of  Suspend- 
Flexibility  Secured  by  means  of  Two  ing  Boiler  of  Small  Diameter. 

Pieces  of  Boiler-Plate  Bolted 
Together. 

of  the  furnace  shall  be  such  as  to  give  the  maximum  results.  No 
boiler  is  economical  the  furnace  of  which  is  so  small  that  the  fire  has 
to  be  forced  to  obtain  the  desired  result.  The  furnace,  of  course,  will 
vary  in  shape,  size,  and  detail  with  the  type  of  boiler  and  the  kind  of 
fuel;  but  certain  essentials — such  as  doors,  grate-bars,  bridge,  and 
ash-pit — are  similar  in  all  furnaces.  To  obtain  the  maximum  effi- 


149 


BOILER  ACCESSORIES 


ciency  of  combustion,  there  should  be  a  uniform  and  abundant  supply 
of  air  to  the  under  side  of  the  grate.  This  is  easily  obtained  when  the 
boilers  are  externally  fired,  but  may  be  somewhat  restricted  when  they 
are  internally  fired.  If  smoky  fuels  are  used,  a  moderate  supply  of 
air  is  necessary  on  the  surface  of  the  coal,  to  prevent  excessive  smoke 
formation;  but,  as  the  air  thus  admitted  is  usually  cold,  the  quantity 
should  be  small,  to  prevent  unnecessary  cooling  of  the  furnace.  This 
air  is  generally  supplied  through  a  draft-plate  in  the  fire-door. 

All  possible  radiation  should,  of  course,  be  prevented.  In  the 
case  of  internally-fired  boilers,  this  radiation  is  not  likely  to  be  exces- 
sive, for  most  of  the  heat  would  have  to  pass  through  the  water  in  the 
boiler  before  radiating,  and  it  is  a  comparatively  easy  matter  to  encase 
such  a  boiler  in  some  sort  of  approved  lagging  which  will  prevent 
most  of  the  heat  from  escaping.  The  case  is  somewhat  different  with 
the  externally-fired  boiler,  where  the  furnace  is  built  in  a  mass  of 
brickwork  below  the  boiler.  In  such  a  furnace  a  considerable  amount 
of  heat  may  radiate  directly  from  the  fire  without  coming  in  contact 
with  the  boiler  or  water  at  all. 

To  allow  for  complete  combustion,  there  should  be  a  sufficient 
space  between  the  grate  and  the  boiler.  In  externally-fired  boilers, 
this  space  may  be  approximately  two  feet.  If  this  distance  is  increased 
beyond  proper  limits,  some  effect  of  the  heat  will  be  lost;  and  if  the 
distance  is  small,  the  plates  are  likely  to  be  damaged,  and  complete 
combustion  impaired.  In  the  internally-fired  boiler,  the  combustion 
space  is  frequently  sacrificed  in  order  to  obtain  a  large  grate  area.  If 
the  space  between  the  grate-bars  and  the  boiler  is  too  small  to  allow 
complete  combustion,  a  combustion  chamber  must  be  provided 
immediately  back  of  the  bridge,  which  will  permit  of  the  complete 
combustion  of  the  gases.  The  ideal  place,  of  course,  for  the  combustion 
chamber,  is  immediately  over  the  grate.  In  locomotive  boilers,  the 
crown  sheet  is  usually  four  to  six  feet  above  the  grate;  but  such  a 
height  is  manifestly  impossible  in  marine  or  other  internally-fired 
boilers,  and  the  combustion  chamber  behind  the  bridge  wall,  in  the 
Scotch  boiler,  partially  compensates  for  the  loss  of  space  immediately 
over  the  grate. 

The  incandescent  fuel  and  unconsumed  gases  should  not  come 
in  contact  with  the  cold  surfaces  of  the  boiler  if  the  most  efficient  com- 


150 


BOILER  ACCESSORIES  9 

bustion  is  desired.  This  condition  is  violated  in  internally-fired 
boilers,  where  the  fire  comes  directly  against  metal  having  water  on  one 
side  of  it.  If  the  flame  is  chilled  by  contact  with  cold  surfaces  before 
the  gases  are  completely  burned,  a  considerable  amount  of  smoke  is' 
likely  to  result. 

The  fire-grate  should  be  of  such  dimensions  that  the  fireman  can 
work  efficiently.  A  grate  more  than  six  feet  long  cannot  be  properly 
taken  care  of  at  the  farther  end ;  and  if  the  grate  is  more  than  four 
feet  wide,  two  fire-doors  should  be  provided.  The  height  of  the  grate 
should  be  laid  out  with  proper  reference  to  the  floor,  two  feet  above 
the  floor  being  about  right.  If  the  grate  is  high,  it  is  difficult,  if  not 
impossible,  to  tend  the  fire  properly.  These  conditions  are  dependent, 
not  so  much  upon  the  boiler,  as  upon  the  physical  limitations  of  the 
fireman,  and  of  course  are  eliminated  by  using  the  mechanical  stoker. 

To  the  above  conditions  may  be  added  a  suitable  temperature  in 
the  fire-room.  No  man  can  tend  a  fire  properly  in  excessive  heat. 
In  stationary  work  it  is  not  difficult  to  maintain  proper  conditions  in 
the  fire-room;  but  at  sea,  where  the  supply  of  air  is  necessarily  limited 
to  what  can  come  in  through  small  openings,  it  is  a  different  problem. 
The  fire  space  on  board  ship  is  small;  and  the  air  coming  through  the 
ventilating  ducts  usually  makes  an  exceedingly  cold  spot  immediately 
under  the  duct  without  producing  much  effect  in  other  parts  of  the 
room. 

Door.  The  furnace  door  is  usually  made  of  cast  iron,  and  is 
supplied  with  a  circular  or  sliding  draft-plate  or  grid,  which  admits 
air  to  the  top  of  the  fire  as  needed.  It  is  usually  protected  by  a  per- 
forated, wrought-iron  baffle-plate  bolted  to  the  door  casting  inside, 
with  an  air-space  of  two  or  three  inches  between.  This  not  only 
protects,  the  cast  iron  of  the  door  from  the  direct  force  of  the  flame, 
but  it  forms  a  chamber  for  the  proper  distribution  of  the  air-supply, 
and  also  helps  to  heat  it  somewhat  before  reaching  the  furnace. 

In  many  of  the  French  torpedo-boats,  a  patent  swinging  door  is 
provided,  set  on  horizontal  hinges  swinging  inwards.  The  door, 
of  course,  must  be  held  open  while  the  stoker  is  tending  the  fire;  but 
in  case  a  tube  blows  out,  it  prevents  the  rapid  escape  of  steam  into  the 
fire-room.  This  is  a  matter  of  much  more  importance  in  the  restricted 
fire-room  commonly  found  on  a  vessel  than  it  would  be  on  land. 

Grate.    The  size  of  grate  will  depend  upon  the  quantity  of  coal 


151 


10  BOILER  ACCESSORIES 

. i. 

likely  to  be  burned.  For  ordinary  draft,  this  may  be  15  Ibs.  or  upward 
per  square  foot  of  grate  surface  per  hour;  for  forced  draft,  40  to  CO 
Ibs. ;  and  in  some  cases  as  much  as  100  Ibs.  per  square  foot  of  grate 
surface  has  been  burned.  If  the  grates  are  long,  they  are  usually 
inclined  slightly  downwards,  say  f  inch  to  the  foot,  which  is  a  great 
assistance  in  firing  and  makes  it  easier  to  keep  fire  on  the  farther  end 
of  the  grate.*  The  grate-bars  are  usually  made  of  cast  iron,  as  this 
material  is  cheaper  than  wrought  iron  and  in  most  instances  lasts  as 
well.  The  bars  are  made  in  various  forms,  according  to  the  fuel 
burned  and  the  shape  of  the  firebox. 

For  large  grates,  the  bars  are  made  singly  or  in  pairs.  For 
smaller  grates,  they  are  made  in  larger  groups.  Grate-bars  should 
not  be  more  than  three  feet  in  length.  The  length  of  grate  can  easily 
be  a  multiple  of  the  length  of  these  bars.  The  bars  have  distance 
pieces  at  the  ends,  and  perhaps  in  the  middle,  to  prevent  distortion. 
They  are  usually  3  inches  or  more  in  depth  at  the  middle,  tapering  to 
perhaps  an  inch  or  so  at  the  ends;  and  the  cross-section  is  slightly 
tapered  from  top  to  bottom,  so  that  the  bars  can  easily  be  withdrawn 
from  the  sand  after  casting.  They  are  usually  made  a  trifle  shorter 
than  the  place  in  which  they  fit,  to  allow  for  expansion,  2  per  cent  of 
the  length  of  the  bar  usually  being  sufficient  for  this  purpose.  The 
air-spaces  between  the  bars  are  usually  about  \  inch  in  width.  For 
burning  pea  coal  or  screenings,  a  finer  grate  must  be  used.  For 
anthracite  coal,  the  space  may  be  a  little  larger.  Bituminous  coal, 
which  readily  cakes,  can  have  a  considerable  space  between  the  bars — 
and  this,  indeed,  is  essential  for  a  proper  supply  of  air. 

Fig.  10  shows  a  circular  grate,  such  as  is  placed  in  a  vertical 
boiler.  J/  shows  the  style  of  grate-bar  used  in  burning  sawdust  or 
shavings;  N  is  what  is  known  as  the  herring  bone  grate;  and  0  is  a 
group  of  bars  of  the  ordinary  form.  In  locomotives,  and  in  boilers 
where  the  grates  are  subjected  to  extra  hard  usage,  wrought-iron  bars 
may  be  used.  The  point  of  fusion  of  wrought  iron  being  higher  than 
that  of  cast  iron,  the  former  would  possess  a  considerable  advantage 
were  it  not  for  the  fact  that  wrought  iron  will  bend  and  twist  more 
readily  than  cast  iron.  Grates  have  been  made  of  hollow  bars, 
through  which  water  is  caused  to  circulate.  By  this  method  their 

*  The  grates  have  an  incline  of  a  few  inches,  so  that  the  bed  of  coal  will  be  thicker 
at  the  rear  than  at  the  front;  this  allows  a  more  even  consumption  of  fuel,  as  the  air 
passes  through  the  tire  at  the  bridge  more  freely. 


152 


BOILER  ACCESSORIES 


11 


durability  is  increased,  and  the  water-grate  forms  a  fairly  good  feed- 
water  heater.     This  type  of  grate,  however,  is  expensive. 


•ate  for 


Fig.  10.    Types  of  Grates  for  Boilers.     V—  Circular  Grate  for  Vertical  Boiler ;  M— Gr 
Burning  Sawdust  or  Shavings;  JV—  "Herring-Bone"  Grate.  O  -Group 
of  Grate-Bars  of  Ordinary  Form. 


Rocking  Grates.  The  labor  of  breaking  the  clinkers  is  con- 
siderable when  ordinary  fixed  grate-bars  are  used;  and  to  economize 
this  labor,  various  forms  of  rocking-grates  have  been  devised.  In 


Fig.  11.    "Kelley  Standard"  Rocking  Grate. 

locomotives,  rocking-grates  are  essential;  and  since  the  rate  of  com- 
bustion is  high,  .the  fire  must  always  be  kept  in  good  condition;  and 


153 


12 


BOILER  ACCESSORIES 


the  grate,  being  below  the  cab  floor,  cannot  easily  be  reached  by  hand. 
Fig.  11  shows  the  "Kelley  Standard"  rocking  grate.  Each  bar  is 
made  up  of  a  number  of  separate  leaves,  which  can  be  removed  and 
replaced  without  renewing  the  whole  bar.  When  the  bar  is  moved 
back  and  forth  by  means  of  a  lever  outside  the  brickwork,  the  leaves 
oscillate  through  a  small  angle  and  break  up  the  clinkers. 

Another  form  of  bar,  shown  in  Fig.  12,  has  proved  very  satis- 
factory. A  and  B  are  two  bars,  the  ends  of  which  are  of  different 
depths.  These  rest  at  each  end  on  a  crank-shaft  C.  As  this  is 
oscillated  by  the  lever  G,  the  alternate  bars  move  up  and  down,  and  the 
clinkers  are  easily  shaken  out. 

Bridge.    The  bridge  is  a  large  wall  or  partition  at  the  back  of  the 


n 


Fig.  12.    Rocking  Grate  Consisting  of  Alternate  Bars  with  Ends  of  Different  Depths 
Resting  oil  a  Crank-Shaft  Oscillated  by  a  Lever. 

grate,  usually  built  of  firebrick  or  cast  iron,  or  of  ordinary  brick 
covered  with  firebrick:  The  bridge  separates  the  grate  from  the  com- 
bustion chamber, .and  causes  the  gases  to  come  in  close  contact  with 
the  boiler  in  passing  into  the  combustion  chamber.  The  proper 
height  of  the  bridge  will  depend  upon  the  draft.  If  the  space  is  nar- 
row between  the  bridge  wall  and  the  boiler,  more  draft  will  be  neces- 
sary to  carry  the  gases  through.  Two  or  more  bridges  may  sometimes 
be  built  in  long  boilers  to  keep  the  gases  in  contact  with  the  shell  as 
long  as  possible. 

Special  Furnaces.  Almost  any  furnace  is  adapted  for  the  use  of 
anthracite  or  bituminous  coal  containing  less  than  20  per  cent  of 
volatile  matter;  but  if  there  is  more  than  this  amount  of  volatile 
matter,  the  heat  is  likely  to  be  so  intense  that  the  fire  should  not  be 


154 


. 


SI 

§5 


BOILER  ACCESSORIES  13 

brought  in  direct  contact  with  the  boiler.  If  the  fuel  should  contain 
40  per  cent  of  volatile  matter,  the  furnace  should  be  surrounded  with 
firebrick  and  should  have  a  high  combustion  chamber.  Coal  is  the 
most  common  fuel  used ;  but  wood,  sawdust,  and  straw  are  not  uncom- 
mon fuels.  When  these  are  burned,  there  should  be  plenty  of  room 
in  the  furnace,  and  a  sufficient  supply  of  air  on  top  of  the  fuel.  Saw- 
dust, shavings,  and  fine  coal  may  be  blown  into  the  furnace  by  an  air- 
blast. 

In  the  West,  crude  petroleum  is  becoming  a  common  fuel.  Ex- 
periments have  shown  that  one  pound  of  crude  oil  is  equivalent  in 
heat  units  to  something  less  than  two  pounds  of  good  coal.  Oil  has 
many  advantages  as  a  boiler  fuel.  It  is  clean,  gives  a  uniform  heat, 
is  economical,  and  requires  much  less  attention  than  coal.  There  are 
no  ashes  to  handle,  and  one  man  can  easily  tend  two  or  three  times 
the  number  of  furnaces  that  he  could  if  burning  coal.  The  fire  can 
be  started  and  stopped  instantly;  and  the  supply  of  air  can  be  so  regu- 
lated that,  unless  the  boiler  js  forced  to  the  limit,  there  will  be  prac- 
tically no  production  of  smoke.  Whether  or  not  oil  is  an  economical 
fuel,  will  depend  upon  the  local  conditions  and  the  market. 

Oil  fuel  is  fed  into  the  furnace  through  a  sprayer  formed,  in 
some  cases  of  two  concentric  conical  tubes.  Compressed  air  or 
steam  entering  through  the  one  tube  draws  the  oil  through  the  other, 
on  the  principle  of  the  atomizer,  and  throws  it  into  the  furnace  in  a 
fine  spray.  For  marine  work,  compressed  air  should  be  used,  as  the 
loss  of  steam  for  this  purpose  would  be  a  matter  of  considerable 
consequence.  Steam,  however,  is  sometimes  used  in  marine  work, 
in  which  case  the  vessel  must  be  equipped  with  an  evaporator  to 
make  up  the  steam  thus  lost.  On  land,  where  fresh  water  is  plenty, 
steam  is  usually  preferred,  arid  is  less  expensive  in  first  cost. 

Prevention  of  Smoke.  In  large  cities,  where  the  escape  of  con- 
siderable quantities  of  smoke  is  undesirable,  several  methods  have 
been  devised  either  to  consume  the  smoke  or  to  prevent  its  formation. 
The  cause  of  smoke,  as  we  have  seen,  is  an  insuffici?ncy  in  the  supply 
of  air,  or  perhaps  a  too  abundant  supply  of  cold  air  above  the  fire; 
or,  again,  smoke  may  be  due  to  the  contact  of  the  flame  with  cold 
surfaces.  An  exceedingly  high  temperature  is  necessary  to  consume 
the  finely  divided  particles  of  carbon,  and  anything  that  tends  to  chill 
the  flame  will  cause  smoke. 


155 


1  \ 


BOILER  ACCESSORIES 


The  actual  loss  caused  by  the  escape  of  smoke,  even  when  it 
is  dense  and  black,  has  been  found  to  be  slight,  and  usually  the  appli- 
ance used  for  prevention  costs  more  than  is  saved.  The  alternate 
firing  of  two  furnaces  which  open  into  a  common  combustion  chamber, 
or  the  alternate  firing  of  two  sides  of  the  same  furnace,  produces  a 
slight  gain  if  the  proper  amount  of  air  is  admitted.  But  if,  in  order 
to  burn  the  smoke,  the  bed  in  one  furnace  or  on  one  side  of  a  furnace 
is  allowed  to  become  thin,  there  will  be  no  gain  in  efficiency. 

The  introduction  of  steam  is  an  efficient  method,  but  it  is  likely 
to  cause  a  too  rapid  rate  of  combustion. 

Another  arrangement  to  prevent  the  escape  of  smoke  is  that  by 


Fig.  13.    "Hawley"  Down-Draft  Furnace  Attached  to  Horizontal  Multitubular  Boiler. 
Note  Upper  Grate  Consisting  of  Water  Tubes  Connected  to  Steel  Drums. 

which  the  coal  is  distilled  in  a  small  furnace  which  is  separate  from  the 
boiler.  The  coke  and  gases  thus  made  are  burned  in  the  furnace  of 
the  steam  boiler.  This  device  is  not  altogether  satisfactory,  on  account 
of  the  loss  of  heat  from  the  detached  furnace.  Rather  than  add  any 
smoke-prevention  device,  anthracite  or  coke  may  be  used  instead  of 
bituminous  coal. 

Many  engineers  and  business  men  consider  a  good  fireman  to  be 
the  best  smoke  preventer. 


156 


BOILER  ACCESSORIES  15 

Down-Draft  Furnaces.  In  order  to  increase  economy  and 
capacity,  or  to  prevent  smoke,  a  down-draft  furnace  is  sometimes 
used.  In  this  type  of  furnace,  there  are  two  grates,  one  a  foot  or  more 
above  the  other.  Fresh  coal  is  fed  to  the  upper  grate,  and,  as  it 
becomes  partially  consumed,  falls  through  to  the  grate  below,  where 
the  combustion  is  completed.  The  draft  is  downward  through  the 
upper  grate,  and  upward  through  the  lower,  because  the  connection 
to  the  chimney  is  from  the  space  between  the  grates.  The  volatile 
gases  are  carried  down  through  the  bed  on  the  upper  grate,  and  are 
burned  in  the 
space  below  it, 
where  they  meet 
the  hot  air  drawn 
upward  from  the 
lower  grate.  A 
large  proportion 
of  the  air  for  com- 
bustion enters  the 
door  at  the  upper 
grate.  Tests  on 

tVip     Hnwlpv     fur     Fi£- 14>    Upper  Grate  of  "Hawley"  Down-Draft  Furnace.    The 
Uie     ndWiey     I  Grate-Bars  are  Water  Tubes  Connected  to  Steel  Drums 

nace  show  that  30 

to  45  pounds  of  coal  per  square  foot  per  hour  can  be  burned  with  good 

results. 

In  the  furnace  made  by  the  Hawley  Down-Draft  Boiler  Com- 
pany, the  grates  are  formed  of  a  series  of  water  tubes  opening  at  the 
ends  into  steel  drums,  shown  in  Figs.  13  and  14,  which  are  connected 
with  the  boiler.  Fig.  13  shows  this  furnace  attached  to  a  horizontal, 
multitubular  boiler.  It  may  be  applied  to  both  tubular  and  water- 
tube  boilers  with  good  results,  and  is  advantageous  to  boilers  of  insuf- 
ficient heating  surface,  and  when  inferior  fuels  are  burned.  It  is 
claimed  that  this  attachment  insures  complete  combustion,  small 
amount  of  ashes  on  account  of  the  second  grate,  good  water  circula- 
tion, and  increased  economy  and  capacity. 

The  Hollow  Arch.  Among  boiler  accessories  specially  adapted 
for  use  on  locomotives  because  of  their  intense  draft,  the  hollow  arch 
has  recently  come  into  prominence.  Its  principle  is  simply  that  of  a 
conduit  providing  a  passage  for  the  admission  of  heated  air  to  the 


157 


16  BOILER  ACCESSORIES 


firebox  above  the  fire,  in  addition  to  the  air  that  comes  up  through 
the  grate  from  below  in  the  ordinary  way.  Its  object  is  to  keep  the 
supply  of  joxygen  at  all  times  sufficient  in  quantity,  and  at  the  proper 
temperature,  to  insure  a  practically  perfect  combustion  of  the  uncon- 
sumed  carbon  and  hydrocarbon  gases  which  are  ordinarily  wasted  and 
lost  in  the  form  of  black  smoke  pouring  from  (he  stack.  It  thus 
insures  an  economy  of  fuel  and  a  proportional  reduction  in  operating 
expense. 

The  problem  of  securing  complete  combu?t?on  of  fuel  on  a  loco- 
motive, is  one  that  presents  peculiar  difficulties.  The  quantity  of 
fuel  to  be  burned  is  so  large,  and  the  firing  space  relatively  so  small, 
that  the  conditions  usually  are  unfavorable  for  economical  combustion. 
A  ton  of  average  bituminous  coal  contains  i-.bout  1,000  pounds  of  pure 
carbon,  700  pounds  of  hydrocarbon  gases,  and  300  pounds  of  non- 
combustible  matter  or  ash.  The  1,700  pounds  Oi  carbon  and  hydro- 
carbons require  about  300,000  cubic  feet  of  air  for  their  complete 
combustion.  In  the  ordinary  method  of  burning  coal  on  a  loco- 
motive, fully  90  per  cent  of  this  air — ov  270,300  cubic  feet  per  ton  of 
fuel  burned — must  be  drawn  up  through  the  grate-bars  and  firebed. 
This  is  practically  impossible  without  forcing  the  draft  to  such  an 
extent  that  the  fire  will  be  pulled  off  the  grates,  and  more  or  less  of  the 
unburned  coal  carried  away  through  the  flues  and  stack.  The  result 
is  that  the  supply  of  air  actually  used  is,  as  a  general  thmg,  insufficient 
for  perfect  combustion,  and  the  combustible  curbon  smoke  and  gases 
pass  out  of  the  stack  without  giving  up  all  of  their  heat  to  the  water 
in  the  boiler.  The  energy  they  contain  is  simply  wasted. 

How,  then,  can  this  be  prevented?  In  other  words,  since  the 
quantity  of  air  that  comes  through  the  grater;  is  insufficient,  how  can 
we  get  enough  air  to  the  fuel  without  interfering  with  the  fire?  It 
must  be  let  in  above  the  fire;  but  it  will  not  do  to  admit  cold  air,  which, 
as  every  fireman  knows,  would  act  as  a  damper  on  the  fire,  retarding 
combustion,  and  increasing  rather  than  preventing  smoke  and  loss 
of  energy.  The  air  to  be  admitted  to  the  fire  must  first  be  heated  to 
as  near  the  ignition  point  as  possible. 

This  is  done  by  means  of  the  hollow  arch.  One  of  these  arches 
of  the  "Wade-Nicholson"  type,  installed  on  a  locomotive,  is  illustrated 
in  Fig.  15,  the  method  of  operation  being  clearly  indicated.  The 
device  may  be  installed  at  both  back  and  front  ends  of  the  firebox. 


168 


BOILER  ACCESSORIES 


17 


The  hollow  passage  through  the  arch  leads  directly  through  suitable 
openings  in  the  firebox  sheets,  from  the  outer  air  to  the  combustion 
chamber,  being  deflected  downward  toward  the  fire  at  the  inner  end. 
The  walls  of  the  arch,  being  highly  heated,  impart  their  heat  to  the  cur- 
rent of  air,  which,  as  it 
emerges  into  the  firebox, is 
practically  at  the  tempera- 
ture of  ignition.  There 
mingling  directly  with  the 
combustible  gases,  an  ap- 
proximately perfect  com- 
bustion  is  established. 
The  resulting  economy  in 
fuel  is  estimated  to  aver- 
age a  saving  of  at  least  8 
per  cent. 

The  Chicago  &  North- 
western   Railway,    has, 

•ift^r  CPWTVS  tpct  arlnnt^rl  Fig.  15.  Wade-Nicholson  Hollow  Arch  Installed  In 
alter  Severe  lest,  adopted  Locomotive  Boiler.  The  Water-Tube  Supports 

arches  of  the  above  type 

on  over  200  of  its  locomotives;  and  its  example  has  been  followed  on 
many  of  the  locomotives  of  the  Santa  Fe,  the  Chicago,  Milwaukee  & 
St.  Paul,  the  Pere  Marquette,  the  Duluth  &  Iron  Range,  and  other 
important  railroads  in  this  country.  In  addition  to  the  saving  in 
fuel,  the  following  advantages  are  claimed  for  the  hollow  arch: 

Being  air-cooled,  its  life  is  two  to  three  times  that  of  the  ordinary  solid 
brick  arch. 

It  does  away  with  the  smoke  nuisance. 

The  air,  being  heated  before  striking  the  combustible  gases,  unites  with 
them  instantly,  giving  a  brighter,  cleaner,  more  intense  fire,  and  resulting 
in  a  better  steaming  engine. 

The  back  arch  acts  as  a  baffle-sheet,  protecting  the  crown  sheet  and 
upper  flues,  and  gives  a  more  uniform  distribution  of  heat  throughout,  re- 
sulting in  less  leaky  flues  and  a  saving  in  boiler  repairs. 

The  arch  can  be  used  either  with  or  without  water-filled  circulating 
arch  tubes  as  supports. 

Arches  can  readily  be  removed  and  reset,  in  whole  or  in  part,  without 
damage,  to  give  access  to  flues  when  repairs  are  needed. 

Fuel  Economizers.  Many  devices  have  been  employed  whereby 
a  portion  of  the  heat  may  be  extracted  from  the  gases  as  they  pass 


150 


BOILER  ACCESSORIES 


160 


BOILER  ACCESSORIES 


19 


from  the  Boiler  to  the  uptake.  Most  of  these  consist  of  a  tubular 
arrangement  through  which  the  hot  gases  pass;  but,  as  these  are  soon 
covered  with  a  thick  deposit  of  soot,  they  quickly  become  inoperative. 
The  "Green"  economizer  (Fig.  16)  solves  this  difficulty  by  means  of 
small  scrapers  which  work  up  and  down  between  the  tubes.  These 
scrapers  are  operated  by  a^small  engine,  and  keep  the  tubes  free  from 
soot.  The  feed-water  is  pumped  through  these  tubes  on  its  way  to 
the  boiler,  and  is  thoroughly  heated.  An  economizer  of  this  sort  will 
extract  40  per  cent  or  more  of  the  heat  from  the  waste  gases;  but  by 
reducing  the  temperature  of  these  gases,  the  draft  is  somewhat  reduced, 
and  either  the  chimney  must  be  built  higher,  or  a  blower  must  be 
used. 

Mechanical  Stokers.  The  mechanical  stoker,  which  feeds  coal 
and  te^ds  fires  by  machinery,  is  coming  more  and  more  into  general  use. 
With  a  good  mechanical  stoker,  one  man  can  tend  several  furnaces 
with  little  labor.  There  are  several  d'fferent  types,  and  in  most  of 
them  the  coal  is  fed  into  a  hopper  of  such  size  that  it  need  not  be  often 
filled.  Some  stokers  work  continuously;  others,  only  when  thrown 

into  gear  by  the 


fireman.  In  the 
"Honey"  stoker 
(Fig.  17),  the 
grate-bars  ex- 
tend across  the 
furnace,  and 
form  a  series  of 
steps  down 
which  the  fuel 
moves.  Each 
grate  bar  is  hung 
on  pivots  at  ths 

ends,  and  is  operated  by  a  rocker-bar.  This  rocker-bar  is  driven  by  a 
small  steam  engine,  with  a  slow,  regular  reciprocation  which  causes 
the  grate-bars  to  tip  so  that  the  coal  of  its  own  weight  slides  from 
one  grate-bar  to  the  next.  Coal  from  a  hopper  falls  onto  a  hori- 
zontal plate,  and  is  fed  into  the  top  of  the  grate  by  a  pusher.  The 
rapidity  with  which  the  fuel  can  be  fed,  is  regulated  by  changing  the 
stroke  of  the  pusher  and  by  governing  the  speed  of  the  engine.  Ashes 


Fig.  17.    Detail  of  "Roney"  Mechanical  Stoker. 


161 


20  BOILER  ACCESSORIES 

and  clinkers  collect  on  the  dumping-grate  at  the  end  of  the  grate-bars, 
whence  they  can  be  dumped  into  the  ash-pit. 

This  type  of  grate  is  well  adapted  for  smoke  prevention,  for  the 
fresh  fuel  fed  in  at  the  top  is  rapidly  coked,  and  the  volatile  gases  are 
easily  consumed.  The  rapidity  of  feed  should  be  so  regulated  that 
no  unburned  fuel  gets  past  the  dump-grate.  If  the  fire  becomes  too 
thin,  there  will  be  a  loss  of  efficiency  due  to  the  excess  of  air  which 
passes  through  the  burning  fuel.  It  is  easy  to  detect  the  loss  from 
too  much  fuel,  but  not  so  easy  if  there  is  too  little  fuel. 

All  mechanical  stokers  in  which  the  movable  parts  are  inside  the 
furnaces,  are  likely  to  get  out  of  order  because  of  the  heat  and  dirt. 

Fusible  Plugs.  Fusible  plugs  are  usually  inserted-  in  the  top 
sheet  or  crown  sheet  of  boilers,  as  a  safeguard  against  collapse  of  the 
furnace  crown  should  the  water  in  any  way  be  drawn  out  of  the  boiler 
while  the  fire  is  burning.  These  plugs  consist  of  a  core  composed  of 
an  alloy  of  tin,  lead,  and  bismuth,  with  a  covering  of  brass  or  cast 
iron.  The  United  States  inspection  law  requires  at  least  one  fusible 
plug  to  be  put  in  every  marine  boiler,  with  the  exception  of  water- 
tube  boilers,  the  plug  to  be  made  of  a  bronze  casing  filled  with  good- 
quality  "Banca"  tin  from  end  to  end.  While  this  plug  is  kept  at  a 
comparatively  low  temperature  by  water  on  one  side,  the  fire  on  the 
other  side  will  not  melt  it;  but  when  the  water-level  becomes  low 
enough  to  leave  one  end  of  the  plug  uncovered,  the  alloy  core  of  the 
plug,  having  a  comparatively  low  melting  point,  will  fuse,  thus  running 
out  of  its  casing,  relieving  the  pressure  in  the  boiler,  and  allowing  the 
excess  of  steam  to  extinguish  the  fire,  which  otherwise  would  be  likely 
to  destroy  the  crown  sheet. 

Fusible  plugs  are  frequently  unreliable.  Sometimes  they  will 
blow  out  when  there  is  no  apparent  cause,  and  sometimes  remain 
intact  when  the  plates  have  become  overheated.  If  a  coating  of  hard 
scale  is  allowed  to  accumulate  over  the  plug,  it  may  stand  consider- 
able pressure,  even  after  the  core  has  become  melted.  To  provide 
against  this,  the  plug  should  be  replaced  frequently.  If  allowed  to 
remain  in  the  boiler  for  any  length  of  time,  the  composition  of  the 
alloy  is  likely  to  change,  the  plug  thus  becoming  more  or  less  unre- 
liable. 

Figs.  18  and  19  illustrate  the  ordinary  plug.  It  should  be  so 
made  that,  when  screwed  into  the  crown  sheet,  it  will  project  1£  or 


162 


BOXLER  ACCESSORIES 


21 


2  inches  above  the  plates,  so  that  when  the  alloy  melts  there  will  be  a 
sufficient  depth  of  water  over  the  crown  sheet  to  prevent  injury  from 
heat. 

Sometimes  the  core  is  covered  with  a  thin  copper  cap,  as  shown 


Pig.  18.  Fusible  Plug.    At  Right  is  Sectional  View  of  Plug  Attached  to  Crowu 

Sheet  of  Boiler,  to  Give  Automatic  Warning  in  Case  of 

Overheating  of  Plates. 

in  Fig.  18,  which  protects  the  alloy  from  contact  with  the  water,  thus 
preventing  a  chemical  change  and  the  formation  of  scale.  It  does 
not  necessarily  follow  that  a  hole  \  inch  or  f  inch  in  diameter  will 


Fig.  19.    Illustrating  Action  of  Fusible  Plug  Attached  to  Crown  Sheet. 

liberate  sttam  fast  enough  t3  prevent  excess  of  pressure.     If  a  small 
quantity  of  steam  is  introduced  into  the  firebox,  it  may  have  the 


163 


BOILER  ACCESSORIES 


effect  of  brightening  the  fire  and  increasing  the  heat  of  combustion, 
owing  to  the  formation  of  water  gas  as  the  steam  mingles  with  the 
burning  coal.  The  steam,  moreover,  might  have  the  effect  of  inducing 
additional  draft.  If,  however,  the  quantity  of  escaping  steam  and 
water  is  considerable,  combustion  will  be  retarded,  and  the  fire  will 
be  partially  extinguished.  It  will  operate  to  warn  the  fireman  of 
what  has  happened;  and  if  the  escape  of  steam  is  not  too  rapid,  he 
may  throw  on  wet  ashes  and  deaden  the  fire. 

NATURAL  AND  FORCED  DRAFTS 

The  draft  in  a  chimney  is  caused  by  the  difference  in  weight 
between  the  volume  of  heated  gases  inside  and  "the  outside  air.  This 
being  so,  it  is  apparent  that  the  taller  the  chimney,  the  greater  this 
difference  will  be.  The  force  or  intensity  of  a  draft  is  increased,  and 
additional  draft  is  induced,  by  the  force  of  the  wind  as  it  whistles  by 


Fig.  20.    "Eames  Differential"  Draft-Gauge. 

the  chimney  top.  The  intensity  may  at  any  time  be  measured  by  a 
draft-gauge.  The  most  satisfactory  instrument  of  this  sort  is  the 
"Eames  Differential"  draft-gauge,  shown  in  Fig.  20.  The  tube  is 
filled  with  a  special  non-drying,  non-evaporating  oil  of  known  specific 
gravity.  The  incline  and  diameter  of  the  tube  are  so  proportioned 
that  the  readings  are  equivalent  to  inches  of  water,  in  which  terms 
the  draft  is  invariably  measured. 

Other  things  being  equal,  the  rate  of  combustion  depends  upon 
the  height  of  the  chimney.  A  chimney  20  to  25  feet  in  height  will 
cause  a  draft  sufficient  to  burn  about  8  Ibs.  of  coal  per  square  foot  of 
grate  area  per  hour.  If  the  height  is  increased  to  about  100  feet, 
the  rate  of  combustion  will  be  increased  to  approximately  15  Ibs.  per 
square  foot;  and  to  burn  25  Ibs.,  the  chimney  should  be  about  175 
feet  high.  This  is  measured  above  the  grate  of  the  boiler.  For  good 
bituminous  or  anthracite  coal,  the  chimney  must  be  higher  than  for 


164 


BOILER  ACCESSORIES  23 

wood,  if  the  same  rate  of  combustion  is  desired.  If  the  boiler  has 
small  or  winding  passages,  the  chimney  must  be  higher  to  produce 
the  same  effective  draft.  High  chimneys  are  costly;  and  it  is  fre- 
quently the  practice  to  build  two  or  three  small  chimneys  in  place  of 
the  big  one,  and  to  supplement  them  with  some  form  of  forced  draft. 

By  means  of  forced  draft,  the  rate  of  fuel  combustion  can  be 
increased  under  favorable  conditions  to  100  Ibs.  of  coal  per  square 
foot  of  grate  surface  per  hour.  This,  of  course,  greatly  increases  the 
power  of  the  plant,  but  is  likely  to  injure  the  boiler,  and  is  uneconomi- 
cal under  most  conditions.  There  are  three  systems  of  forced  draft 
in  common  use: 

1.     The  closed  stokc-hold,  as  used  in  marine  work; 

2»     The  closed  ash-pit', 

3.     The  induced  draft. 

Closed  Stoke-Hold.  One  of  the  most  common  forms  of  forced 
draft,  especially  as  used  on  warships,  is  obtained  by  closing  the  stoke- 
holds and  blowing  a  fresh  supply  of  air  into  the  fire-room.  This  gives 
an  exceedingly  good  ventilation  and  keeps  the  fire-room  in  good  con- 
dition; but  its  chief  objection  is  that  when  the  furnace  doors  are 
opened  there  is  a  tremendous  indraft  of  cold  air,  which  tends  to  lower 
the  efficiency  of  the  boiler.  If  this  system  is  employed,  the  bulk- 
heads adjacent  to  the  boiler-room  must  be  provided  with  double  doors, 
forming  an  air-lock  between.  By  opening  only  one  door  at  a  time,  the 
pressure  in  the  fire-room  is  not  lost.  This  system  seems  to  possess 
but  one  distinct  advantage,  and  that  is  coolness  and  therefore  comfort 
for  the  firemen;  but  the  disadvantage  of  the  inrush  of  air  to  the 
furnaces  when  firing,  is  sufficient,  in  some  cases,  to  make  the  system 
questionable. 

Closed  Ash-Pit.  The  essential  features  of  forced  draft  by  this 
method  consist  merely  in  closing  the  ash-pit  tight,  and  blowing  the  air 
directly  under  the  grate.  When  the  fires  are  cleaned,  the  draft,  of 
course,  must  be  shut  off;  otherwise  the  flames  will  be  blown  out  into 
the  fire-room.  The  fire-room,  under  this  system,  is  likely  to  be 
hotter  than  by  the  other  method ;  but  this  system  would  seem  to  be  the 
better  from  a  mechanical  point  of  view. 

-  There  are  several  patented  devices  in  connection  with  the  forced 
draft,  of  which  the  "Howden"  and  the  "Ellis  and  Eaves"  systems 
may  be  specially  mentioned.  It  may  be  worth  while  to  note  that  if  fuel- 


185 


24  BOILER  ACCESSORIES 


oil  is  burned,  any  one  of  these  systems  of  forced  draft  will  work  better 
than  with  coal,  for  the  fire  can  be  tended  without  opening  the  fire- 
doors. 

Induced  Draft.  Perhaps  the  most  common  example  of  induced 
draft  is  to  be  found  in  the  locomotive,  where  the  exhaust  steam  is 
turned  into  the  smokestack.  The  rush  of  tnis  steam  up  the  stack, 
by  carrying  a  large  volume  of  air  with  it,  induces  a  tremendous  draft. 
Induced  draft  may  also  be  obtained  in  stationary  and  marine  plants 
by  placing  a  blower  in  the  chimney  or  stack.  In  marine  work,  of 
course,  induced  draft  by  exhaust  steam  is  out  of  the  question.  When 
a  blower  is  placed  in  the  smokestack,  an  economizer  should  be  used, 
so  that  the  gases  may  be  cooled  before  they  reach  the  blower.  The 
draft  obtained  on  locomotives  is  frequently  equivalent  to  a  column 
of  five  or  six  inches  of  water;  while  a  forced  draft  of  two  inches  is 
usually  considered  large,  except  for  torpedo-boats,  which  may  have 
as  strong  a  draft  as  a  locomotive  has. 

Howden  System.  The  Howden  system  of  forced  draft  with 
closed  ash-pit  has  been  used  to  a  considerable  extent  in  both  mer- 
cantile and  naval  service.  The  air  supplied  to  the  ash-pit  is  first 
heated  by  passing  through  a  heater  in  the  uptake.  Waste  gases  pass 
through  tubes;  and  the  air,  passing  among  them  before  entering  the 
furnace,  is  heated  to  a  high  temperature.  A  consumption  of  60  Ibs. 
of  coal  per  square  foot  of  grate  is  easily  obtained  with  this  system; 
and  care  must  be  taken  that  the  fire  is  not  forced  too  hard,  as  there  is 
more  danger  of  burning  out  the  grate  than  if  the  air-supply  is  not 
heated. 

Ellis  and  Eaves  System.  Heating  the  air  does  not  necessitate  its 
being  forced  into  the  closed  ash-pit,  for  it  is  quite  feasible  to  heat  the 
air  in  connection  with  draft  induced  by  an  exhaust  fan  at  the  base  of 
the  funnel.  Such  is  the  Ellis  and  Eaves  system.  This  system  was 
first  tried  in  the  boiler  shops  at  the  works  of  the  John  Brown  Company, 
in  Sheffield,  England,  and  was  later  adopted  on  many  vessels.  The 
Ellis  and  Eaves  heater  is  fixed  on  top  of  the  boilers,  and  is  divided 
into  two  parts  separated  at  the  front  by  a  smoke-box  and  at  the  back 
by  a  funnel.  The  hot  gases,  therefore — which  pass  outside  the  tubes — 
have  to  take  a  somewhat  circuitous  course;  while  the  passage  of  the 
air  to  be  heated,  on  the  contrary,  takes  a  direct  course.  The  dis- 
tribution of  air  to  the  ash-pit  is  similar  to  that  of  the  Howden  system. 


166 


BOILER  ACCESSORIES  25 

The  advantages  of  this  system  lie  in  the  general  convenience  of  the 
induced  draft  and  the  absence  of  jets  of  hot  air  shooting  out  into 
the  boiler-room.  The  draft  need  not  be  shut  off  when  stoking  the 
fires,  unless  it  is  desired  to  prevent  the  inrush  of  air  already  referred  to 
under  the  general  discussion  of  "closed  stoke-holds."  The  air  in  the 
fire-room  being  of  a  relatively  higher  temperature  than  would  obtain 
with  closed  stoke-holds,  and  the  quantity  being  much  less,  this  objec- 
tion has  no  great  weight.  With  the  Howden  system  it  is  necessary 
that  the  doors  should  be  tight;  otherwise  hot  air  will  be  blown  out 
Into  the  fire-room.  With  this  system  a  few  leaks  are  of  no  conse- 
quence, and  the  fire-room  will  be  somewhat  cooler  than  with  the 
Howden  System.  The  objections  to  the  Ellis  and  Eaves  system  are 
these  inherent  in  any  system  of  draft  induced  by  a  fan — that  is  to  say, 
a  poor  efficiency  of  the  fan  working  in  heated  gases,  and  lost  work  in 
drawing  air  through  tortuous  passages. 

Steam  Jets.  Steam  jets  may  be  used  for  inducing  a  draft.  They 
may  be  placed  either  in  the  smokestack,  or  below  or  above  the  grate ; 
but  in  general  they  are  not  so  economical  as  a  fan  used  for  the  same 
purpose.  In  locomotives  and  fire-engines,  where  the  exhaust  steam 
is  at  high  pressure,  an  intense  draft  may  be  induced  by  exhausting 
this  up  the  smokestack.  In  both  these  cases,  the  saving  of  weight 
due  to  the  use  of  a  small  boiler  running  at  high  tension,  is  of  greater 
practical  importance  than  the  economy  of  fuel;  and  for  such  purposes 
this  arrangement  is  entirely  satisfactory. 

A  steam  jet  may  be  used  directly  in  the  furnace,  either  above  or 
below  the  grate.  The  steam  enters  through  a  small  pipe,  and  ex- 
pands through  a  nozzle  surrounded  by  an  annular,  funnel-shaped 
tube.  The  escape  of  steam  from  the  inner  nozzle  draws  in  a  large 
volume  of  air  through  the  outer  tube,  and  produces  an  intense  draft. 
If.steam  is  blown  into  the  ash-pit  in  this  manner,  it  forms  a  sort  of 
producer  gas  by  mingling  with  the  incandescent  fuel,  and  materially 
aids  in  the  combustion  of  cheap  and  apparently  worthless  fuel.  Al- 
most as  poor  fuel  can  be  successfully  used  with  this  arrangement  as 
can  be  used  in  the  grates  of  the  down-draft  furnaces.  Such  arrange- 
ments have  given  excellent  satisfaction,  and  the  production  of  smoke 
is  materially  lessened. 

Some  tests  made  in  the  French  Navy  some  years  ago,  showed 
that,  with  the  use  ^  the  steam  jet  above  the  grate,  the  coal  con- 


167 


BOILER  ACCESSORIES 


sumption  per  square  foot  of  grate  area  could  readily  be  doubled; 
but  this  result  would  be  attained  at  the  expense  of  fuel  economy; 
for,  while  with  natural  draft  one  pound  of  coal  produced  approxi- 
mately eight  pounds  of  steam  which  could  be  used  by  the  engine, 
with  a  steam  jet  less  than  6|  pounds  of  steam  per  pound  of  coal  was 
available  for  like  purposes.  The  total  evaporation  per  pound  of  fuel 
was  approximately  the  same  in  each  case,  the  difference  being  the 
quantity  of  steam  used  in  the  jet.  If  a  steam  jet  is  used  on  board 
ship,  it  consumes  a  considerable  amount  of  fresh  water,  which  must 
be  replaced  by  evaporators,  or  by  the  use  of  salt 
water,  which  is  decidedly  objectionable. 

TUBE=CLEANERS 

To  secure  the  best  results  from  a  boiler,  the 
tubes  should  be  kept  thoroughly  clean.  The  collec- 
tion of   soot  on  the  tubes  is  as  detrimental  to 
economy  as  the  formation  of  boiler  scale.  The  soot 
may  be  removed  by  the  insertion  of  brushes  when 
the  boiler  is  not  under  steam,  or  the  tubes  may 
be  blown  out  with  a  steam  jet   designed  for  this 
purpose.  Fig.  21  illustrates  forms  of  tube-cleaners, 
of  which  there  are  numerous  types  on  the  market. 
The  type  shown  at  B  is  de- 
signed for  use  with  a  steam 
jet.  In  the  case  of  oil-burn- 
ing locomotives,   the  tubes 
are  usually  cleaned  with  the 
aid  of  a  sand-blast. 

TUBE-STOPPERS 

Fl«.  21.    Types  of  Tube-Cleaners.  jt    frequently    happens, 

when  tubular  boilers  are  under  pressure,  that  leaks  occur  in  the 
tubes  through  pitting,  defective  welding,  or  the  development  of 
cracks.  Formerly,  when  this  occurred,  the  fire  was  drawn,  and  tin. 
ends  of  the  tube  plugged  with  hardwood  bungs  driven  hard  home  or 
with  iron  plugs  calked  in.  With  high  pressures,  such  procedure  is 
impossible.  Tube-stoppers  used  for  high  pressure  are  joined  to- 
gether by  a  tie-bar  of  some  sort.  They  are  usually  wedge-shaped ;  and 


168 


BOILER  ACCESSORIES 


27 


the  tie-rod,  passing  through  the  stopper  at  one  end,  with  a  plug  at  the 
other  end,  can  be  screwed  hard  up. 

The  simplest  form  of  stopper  has  to  be  inserted  from  the  rear,  and 
necessitates  drawing  the  fire;  but  Fig.  22  illustrates  a  stopper  which 
can  be  inserted  without  drawing  the  fire.  At  the  end  of  the  rod  is 
hinged  a  folding  bung,  which  can  be  passed  through  the  tube  and 


Fig.  22.    Tube-Stopper  Designed  for  Insertion  without  Drawing  Fire. 

which  opens  out  in  the  combustion  chamber  before  being  pulled  into 
position.  At  the  smoke-box  end  of  the  boiler,  an  india-rubber 
washer,  pressed  between  two  pieces  of  metal,  affords  temporary 
protection  while  the  plug  is  being  put  in  position.  The  stopper  can 
then  be  screwed  up  tightly  with  a  handle  provided  for  that  purpose. 
Fig.  23  illustrates  another  arrangement  which  can  be  inserted 
in  the  leaky  tube  without  drawing  the  fire.  The  ends,  being  in  the 


160 


28 


BOILER  ACCESSORIES 


form  of  stuffing  glands,  press  an  asbestos  packing  hard  against  the 
side  of  the  tube. 


Fig.  23.     Another  Type  of  Tube-Stopper  Used  without  Drawing  Fire.    As  the  Parts  are 
Screwed  Up,  the  Asbestos  Packing  is  Driven  Hard  against  Side  ef  Tube. 

MANHOLES  AND  HANDHOLES 

A  manhole  allows  access  to  the  boiler  for  cleaning  and  repairs. 
It  is  usually  elliptical  in  form  and  large  enough  to  admit  a  man. 
About  16  inches  for  the  major  axis,  and 
12  for  the  minor  axis,  is  a  good  size. 
The  manhole  is  closed  by  a  plate  or 
cover  made  of  cast  or  wrought  iron. 
This  plate  is  held  to  the  seat  by  a  yoke 
or  yokes,  and  bolts.  Fig.  24  shows  one 
form,  Y  being  the  yoke,  L  the  cover, 
and  .ZV  the  bolt.  The  joint  between 
the  cover  and  the  shell  is  made  steam 
tight  by  packing. 

The  strength  of  the  boiler  should 
always  remain  unimpaired;  so,  when- 
ever a  large  hole  is  cut  in  the  plate, 
the  eclge  should  be  strengthened,  for 
the  tension  is  concentrated  there,  and 

the  plates  are,  moreover,  likely  to  become  weak  by  corrosion.  The 
strain  put  upon  the  plate  by  screwing  up  the  cover,  if  no  packing 
is  used,  is  considerable,  especially  if  a  piece  of  scale  gets  between  the 
faces  and  the  joint  is  then  made  tight. 


L 

170 


BOILER  ACCESSORIES  29 

Fig.  25  shows  the  section  of  a  strong  and  simple  manhole.  The 
edge  of  the  plate  is  strengthened  by  a  broad  ring  of  steel,  which  is 
flanged  and  riveted  to  the  shell,  its  edge  forming  the  seat.  The  cover 
as  shown  in  the  figure  is  shaped  for  strength.  The  edge  of  the  ring 
which  forms  the  seat,  and  the  cover,  are  machined  to  make  a  tight  joint 
without  packing.  The  strengthening  ring  should  be  at  least  §  inch 
thick  and  4  inches  wide,  that  the  rivet-holes  may  not  be  too  near  the 
edge. 

Handholcs  and  mudholes  are  more  commonly  placed  in  boilers, 
which  are  so  constructed  that  a  man  cannot  enter— in  a  vertical  boiler, 
for  example.  They  are  used  to  some  extent  in  other  boilers;  in 
horizontal  return-tube  boilers  there  is  usually  a  handhole  in  each  end, 


Fig.  25.    Section  of  a  Strong  but  Simple  Type  of  Manhole. 

near  the  bottom.  Handholes  are  very  convenient  to  admit  hose  for 
washing  out  the  boiler,  also  for  removing  scale  and  sediment.  Hand- 
holes  are  similar  to  manholes  in  construction,  but  require  only  one 
yoke  and  one  bolt  to  keep  them  in  place.  Mudholes  should  be  pro- 
vided in  order  that  the  sediment  and  detached  scale  can  be  removed 
without  lifting  the  accumulated  mass  to  the  top  manhole.  Mudholes 
and  handholes  greatly  facilitate  cleaning  the  fire-box  water-leg  of 
locomotive  and  small  vertical  boilers. 

STEAM  AND  VACUUM  GAUGES 

The  steam  pressure  in  the  boiler  is  measured  in  pounds  per 
square  inch.  When  we  say  the  boiler  is  working  or  steaming  at  80 
pounds'  pressure,  we  mean  that  the  gauge  pressure  is  80  pounds;  that 
is,  the  pressure  in  the  boiler  is  80  pounds  above  atmospheric  pressure. 
It  could  be  measured  by  a  water  or  mercury  column;  but,  as  these 
would  need  to  be  very  high  to  measure  the  pressures  used  at  the  present 
day,  they  are  not  practicable,  and  so  a  spring-pressure  gauge  is  used 
instead. 

The  dial  gauge,  now  used  almost  universally,  was  invented  by 
M.  Bourdon.  It  is  designed  in  accordance  with  the  principle  that  a 


171 


30 


BOILER  ACCESSORIES 


flattened,  curved  tube  closed  at  one  end   tends   to   become   straight 
when  subjected  to  internal  pressure. 

The  tube,  which  is  usually  oval  in  section,  is  bent  into  the  arc 
of  a  circle  as  shown  in  Fig.  26.  One  end  is  fixed,  and  is  in  com- 
munication with  the  boiler.  The  other 
is  closed  and  free  to  mQve.  By  means 
of  levers,  a  curved  rack,  and  a  pinion, 
the  motion  of  the  free  end  is  multiplied 
and  indicated  by  a  needle,  which  is 
attached  to  the  pinion.  The  needle 
moves  over  a  dial  which  is  graduated 
to  agree  with  a  mercury  column,  or 
with  a  standard  gauge.  The  back-lash 
of  the  levers  is  taken  up  by  a  hair 
spring.  Fig.  27  shows  the  interior  and 
face  of  a  Bourdon  steam  gauge  manu- 
factured by  the  American  Steam  Gauge 
Company. 

Fig.  28  shows  the  exterior  and  interior  of  a  steam  gauge  with 
a  light  tube  for  low  pressures;  the  face  of  the  dial  is  graduated  corre- 
sponding to  the  mercury  column.  The  only  difference  between  this 
gauge  and  the  vacuum  gauge,  is  that  in  the  latter  the  curved  tube  is 


Fig.  2(5.     Steam-Filled  Curved  Tube 
Indicating  Pressure  in  Bour- 
don Steam  Gauge. 


Fig.  27.    Interior  Mechanism,  and  Dial,  of  "Lane"  Type  of  Steam  Gauge. 

turned  in  the  opposite  direction  so  that  the  needle  will  move  clockwise 
with  a  decrease  of  pressure. 


172 


BOILER  ACCESSORIES 


31 


On  account  of  the  jarring,  the  gauge  for  locomotives  must  be 
very  strong.  To  prevent  excessive  vibration  of  the  needle,  two  short, 
stiffer  springs  are  used,  as  shown  in  Fig.  29. 


Fig.  28.    Interior  Mechanism,  and  Dial,  of  Low-Pressure  Steam  Gauge. 

Sometimes  two  pressure  gauges  are  fitted  to  a  boiler,  one  indicating 
the  working  pressure,  and  the  other  graduated  to  about  twice  the  work- 
ing pressure.  The  latter  is  useful  in  testing  the  boiler  under  water 
pressure,  and  also  serves  as  a  check  on  the  other.  The  pipe  which  con- 
nects the  pressure  gauge  to  the  boiler  should  have  bends  in  it  near  the 
gauge.  These  bends — or,  better,  a  coil  pipe,  as  shown  in  Fig.  30 — 


Fig.  29.    Steam  Gauge  for  Use  on  Locomotives.    Excessive  Vibration  of  Needle 
Prevented  by  Use  of  Two  Short,  Stiff  Springs. 

are  filled  with  water,  which  transmits  pressure  and  keeps  the  spring  at 
a  nearly  constant  low  temperature.     Gauges  should  be  placed  where 


173 


32 


BOILER  ACCESSORIES 


the  water  in  the  coiled  pipe  will  not  freeze;  also,  the  gauge  should 
not  be  exposed  to  strong  heat.     In  order  that  the  gauge  may  be 


Fig.  30.    Water  Pilled  Coil  Pipe  for  Connection  to  Steam  Gauge.    The  Water 
Transmits  Pressure  and  Regulates  Temperature. 

removed  from  the  boiler  for  examination,  repairs,  or  calibration, 
when  the  boiler  is  under  pressure,  the  connection  should  be  provided 
with  stop-cocks. 

In  a  battery  of  boilers,  each  should  have  its  pressure  gauge,  which1 
should  be  connected  directly  to  the  boiler,  not  to  the  steam  pipe. 

WATER  GAUGES 

It  is  of  great  importance  that  the  level  of  the  water  in  the  boiler 
can  easily  be  ascertained  at  all  times.     Should  the  level  be  too  low, 

there  is  danger 
o  f  overheating 
the  furnace  plates 
or  tubes.  If  it  is 
too  high,  there  is 
likely  to  be  an 
undue  amount  of 
priming.  The 
water-level  is 
usually  indicated 
by  gauge-cocks 
or  try-cocks  or 
water  gauge- 
glasses.  Some- 
Fig.  31.  Ordinary  Form  of  Try-Cock  for  Determining  Water-  times  a  float  IS 
Level  in  Boiler. 

provided,    which 
is  connected  to  a  small  whistle,  and  if  the  water-level  falls  below  a 


174 


BOILER  ACCESSORIES 


33 


Fig.  32.    Try-Cock  Operated  by  Means  of  Lever. 


certain  point,  an  alarm  is  sounded.     Such  a  device  can  readily  be 

used  in  conjunction  with  the  ordinary  water-gauge. 

Try -Cocks.    Try-cocks   are  very  generally  used.     They  are  of 

widely  different 
forms,  and  may 
be  either  like  the 
general  type 
shown  in  Fig.  31, 
which  is  the  ordi- 
nary 1  o  c  o  m  o- 
tive  form,  con- 
structed in  two 

parts  so  that  they  can  be  separated  for  the  purpose  of  repacking 

without  detachment  from  the  boiler;   or 

they  may  be  of  the  lever  type  shown  in 

Fig.  32.     There  are  usually  three  cocks, 

one  at  the  highest  desired  water-level,  one 

at  the  lowest,  and  one  midway.       More 

cocks  may,  of  course,  be  used  if  desired. 

The    water-level   can   be   determined  by 

opening  the  cocks  in  succession  and  ob- 
serving whether  dry  steam  or  hot  water 

flows  out.      If  the  boiler  is  encased  in 

brickwork,  as  is  customary  for  externally- 
fired  boilers,  the  gauge-cocks  are  placed 

outside  the  brickwork,  and  are  connected 

to    the   boiler  by  nipples  of  the  proper 

length. 

Gauge-Glasses.      In   order   that   the 

fireman  may  know  the  water-level  without 

trying  the  cocks,  a  water  gauge-glass  is 

used.      It  consists  of  a  strong  glass  tube 

about  one  foot  in  length,  having  the  ends 

connected  to  the  boiler  by  suitable  fittings. 
As  both  ends  of  the  tube  are  in  com- 
munication with  the  boiler,  the  water-level 

in  the  glass  will  be  the  same  as  in  the 

boiler,  and  is  always  in  sight.    Fig.  33  shows  a  good  form  of  gauge- 


Fig. 


A  Good  Type  of  Water 
Gauge-Glass. 


1T5 


BOILER  ACCESSORIES 


glass.  The  glass  is  protected  by  rods  which  are  parallel  to  it.  As 
the  glass  frequently  needs  cleaning,  repacking,  or  renewing,  cocks 
are  provided  for  shutting  off  communication  with  the  boiler.  A 
drain-cock  is  also  placed  at  the  lower  end  to  empty  the  glass  when  the 
attendant  wishes  to  ascertain  whether  the  glass  is  working  properly 
or  not.  The  drain-cock  is  often  provided  with  a  drain-pipe.  The 
steam  and  water  passages  should  be  at  least  one  half-inch  in  internal 
diameter. 

The  glass  is  likely  to  break  because  of  accident  or  of  changes  in 
temperature.  To  prevent  serious  injury  to  the  fireman  and  loss  of 

water  as  a  result  of  the 
breaking  of  the  gauge- 
glass,  automatic  valves 
may  be  placed  in  the 
passages.  In  Fig.  34 
the  ball-valve  is  shown 
in  detail.  If  the  glass 
breaks,  the  pressure  of 
the  steam  drives  the 
ball  outward,  filling 
the  conical  passage. 
When  a  new  glass  is 
put  in,  the  balls  are 
forced  back  by  slowly 
screwing  in  the  stems. 
This,  like  other  safety 
devices,  is  very  likely 
not  to  work  when  it 
should. 

In  boilers  where  the  steam  space  is  small,  as  in  locomotives,  the 
allowable  variation  of  water-level  is  slight;  but  the  greater  care  with 
which  the  glass  is  watched  makes  up  for  the  small  margin  of  safety. 
If  dirty  water  is  used,  or  if  the  water  foams,  the  level  in  the  glass  will 
be  unsteady  and  unreliable,  since  dirt  clogs  the  passages,  unless  they 
are  large,  and  the  foaming  causes  a  fluctuation  of  the  water-level.  A 
small  pipe  connecting  with  the  steam  space  where  no  ebullition  occurs, 
will  insure  a  steadier  water-level.  If  the  steam  and  water  connection^ 
are  long,  the  pipes  should  be  made  large. 


Fig.  34.    Automatically  Acting  Ball- Valve  to  Prevent 

Injury  to  Workmen  and  Loss  of  Water  on 

Breaking  of  Gauge-Glass. 


176 


BOILER  ACCESSORIES 


35 


The  chief  objection  to  the  gauge-glass — namely,  its  breaking — 
may  be  to  some  extent  overcome  by  attaching  the  gauge-glass  to  a 
gauge-column,  which  is  usually  made  of  brass  and  stands  quite  clear 


Fig.  35.    Ordinary  Water  Gauge-Glass  Supplemented  (alright)  by  "Kllnger 
Patent"  Gauge-Glass. 

of  the  boiler  itself.  In  such  an  arrangement  as  this,  the  temperature 
in  the  gauge-glass  cannot  vary  so  widely  as  if  it  were  attached  directly 
to  the  boiler.  The  "Klinger  Patent"  water  gauge-glass  is  not  easily 
broken,  and  possesses  many  advantages  over  the  common  glass. 
Fig.  35  illustrates  both  these  devices. 

The  water  gauge  is  not  absolutely  reliable,  for  the  water  in  the 
gauge,  being  cooler  than  that  in  the  boiler,  may  not  indicate  the  true 
level,  and  the  small  passages  leading  to  it  may  become  choked  with 


177 


36 


BOILER  ACCESSORIES 


sediment.     If  the  gauge-glass  is  frequently  blown  out  by  the  engineer 
and  kept  clean,  this  difficulty  will  be  reduced  to  a  minimum. 

VALVES 

Of  all  boiler  accessories,  perhaps  the  most  important  are  the 
cocks  and  valves  by  means  of  which  the  flow  of  steam  or  water  may 
be  shut  off  completely  or  partially.  The  valve  operates  by  moving 
a  disc  across  the  pipe  in  a  transverse  direction,  or  by  bringing  a  cap 


Fig.  36.    Ordinary  "Competition"  Type  of 
Globe  Valve. 


Fig.  37.    Globe  Valve  with  Detachable 

Cap  and  Removable  Interior  Disc 

of  Comparatively  Soft  Material 

to  Insure  Tightness. 


tight  upon  the  seat  in  a  fore-and-aft  direction.  A  cock  consists  of  a 
block  inserted  in  the  passageway,  with  an  opening  cut  through  in  one 
direction.  When  the  handle  of  the  cock  is  in  line  of  the  pipe,  the 
opening  allows  the  steam  to  pass  through;  but  if  turned  crosswise,  the 
opening  is  closed. 

The  Globe  Valve.  The  valve  shown  in  Fig.  36  gets  its  name  from 
the  globular  shape  of  the  casing  which  encloses  the  valve.  Extending 
across  this  whole  casing  is  a  substantial  diaphragm,  the  central  portion 


178 


BOILER  ACCESSORIES 


37 


of  which  is  in  a  plane  parallel  with  the  length  of  the  pipe.  The  open- 
ing is  cut  in  this  portion,  horizontal  in  the  figure,  through  which  steam 
or  other  fluid  may  pass  when  the  valve  is  opened.  When  the  valve  is 
closed,  a  cap  is  forced  down  to  close  its  opening.  The  rim  around 
the  opening  is  known  as  the  valve-seat.  The  valve-cap  is  operated  by 
a  spindle,  which  passes  through  the  bonnet  of  the  valve  and  is  mounted 
at  the  upper  end  by  a  small  wheel  or  handle.  To  prevent  the  escape 
of  steam  around  this  spindle,  a  stuffing-box  is  provided.  The  valve- 
cap  may  or  may  not  rotate  as  the  spindle  turns;  usually  it  does  not. 
The  valve  shown  in  Fig.  36  is  the  ordi- 
nary globe  valve  known  to  the  trade  as 
the  "Competition"  valve.  It  is  the 
cheapest  valve  of  the  type,  and  is  not 
satisfactory  where  absolutely  tight  work 
is  required.  If  the  cap  becomes  scored, 
the  valve  will  leak  and  is  then  worthless. 

A  valve  shown  in  Fig.  37  has  a 
detachable  valve-cap;  and  instead  of 
relying  for  tightness  upon  the  valve 
and  seat  coming  together,  metal  to 
metal,  a  removable  disc  is  provided, 
which  being  softer  than  the  metal  valve- 
seat,  easily  takes  up  the  wear,  and  the 
valve  not  only  can  be  closed  tighter, 
but  if  anything  happens  so  that  the 
tightness  of  the  valve  is  impaired,  the 
valve-cap  can  be  replaced  by  another 
at  a  trifling  expense.  In  the  cheaper 
valve,  when  the  cap  is  scored,  the  valve 
is  worthless.  The  valve-seat  sometimes  has  a  slight  bevel,  the  valve- 
cap  being  shaped  like  the  frustum  of  a  cone. 

It  is  impossible  to  close  a  valve  tightly  if  the  slightest  particle 
of  scale  or  grit  gets  between  the  disc  and  the  seat.  If  this  happens, 
the  valve-seat  is  likely  to  become  scored  so  that  it  does  not  hold  tight ; 
but  it  may  be  reground,  and  if  the  valve  disc  itself  is  damaged,  it  can 
readily  be  replaced. 

Angle  Valves.  An  angle  valve,  shown  in  Fig.  38,  is  constructed 
in  a  similar  manner  to  the  ordinary  globe  valve,  and  is  sometimes 


Fig.  38.     Angle  Valve  of  Ordinary 
Globe  Pattern. 


179 


38 


BOILER  ACCESSORIES 


used  in  place  of  the  straightway  valve  and  an  elbow.  Both  these 
styles  of  valve  should  be  so  placed  in  the  steam  pipe  that  the  entering 
steam  comes  beneath  the  valve-seat.  If  this  is  done,  the  valve-stem 
may  easily  be  repacked  simply  by  closing  the  valve.  If  the  steam 
enters  in  the  opposite  direction,  a  leaky  valve-stem  cannot  be  packed, 
as  loosening  the  stuffing-box  would  per- 
mit the  escape  of  the  steam. 

The  Gate  Valve.  The  gate  or 
straightway  valve  gives  a  straight  pas- 
sage through  the  pipe,  and,  when  open, 
offers  very  little  resistance  to  flow.  The 
globe  valve,  of  course,  offers  much  re- 
sistance, because  the  fluid  has  to  change 
its  direction  of  flow  completely. 

There  are  two  forms  of  gate  valve — 
one  with  wedge-shaped  sides,  and  the 
other  having  the  valve  sides  parallel. 
Fig.  39  shows  a  "Chapman"  valve  with 
wedge-shaped  sides.  A  collar  holds 
the  valve  spindle  at  a  fixed  point;  and 
to  open  or  close,  the  valve  is  drawn  up 
or  lowered  by  turning  the  spindle.  When 
the  gate  reaches  the  bottom  of  the  pipe, 
a  wedge  on  the  lower  end  of  the  spindle 
causes  the  sides  to  move  laterally,  with 
sufficient  force  to  bring  a  strong  pres- 
sure against  the  valve-seat.  For  heavy 
work,  these  valves  are  made  with  a  rising  spindle  instead  of  a 
stationary  one.  This  possesses  the  distinct  advantage  of  indicating 
at  a  glance  whether  they  are  opened  or  closed,  while  one  cannot  tell 
by  looking  at  the  ordinary  gate  valve  whether  it  is  open  or  not. 

Check-Valves.  When  it  is  necessary  that  the  flow  should  always 
take  place  in  the  same  direction,  as  in  the  feed-pipe  of  a  boiler,  check- 
valves  are  used.  There  are  several  forms  shown  in  Fig.  40,  one  of 
which  has  a  similar  pattern  to  a  globe  valve,  with  a  ball  or  flat  valve, 
the  seat  being  parallel  to  the  direction  of  flow.  The  valve  is  held  in 
place  by  its  own  weight,  and  by  the  pressure  of  the  fluid  in  case  of  a 
reverse  flow.  In  the  swinging  check-valve,  the  se«t  is  at  an  angle 


Fig.  39.    "Chapman"  Gate  Valve 
with  Wedge-Shaped  Sides. 


180 


BOILER  ACCESSORIES 


39 


of  about  45  degrees  to  the  direction  of  flow.  It  is  fitted  somewhat 
loosely  where  it  is  fastened  to  the  swinging  arm,  so  that  it  may  prop- 
erly seat  itself.  This  form  is  usually  preferred,  as  it  offers  less 
resistance  to  flow  and  there  is  less  chance  for  impurities  to  lodge  on 
the  valve-seat.  When  a  check-valve  is  used  in  the  boiler-feed  pipe, 


ABC 
Fig.  40.    Types  of  Check- Valves.    ^1-Ball- Valve ;  ^-Flat  Valve;  C'-Swiugiiig  Check- Valve. 

there  should  be  a  stop-valve  between  it  and  the  boiler,  which  can  be 
shut  in  case  the  check-valve  should  get  out  of  order. 

Materials.     For  pressures  under  200  Ibs.  per  square  inch,  cast 
iron  may  be  used  for  the  body  of  the  valve;   but,  for  economy,  it 
should  be  used  only  when  the  pressure  is  over  130  Ibs.     For  heavy 
work  it  is  frequently  necessary  to  have  a  massive  valve  that  cannot 
easily  be  broken.     In  such  a  case  a  cast-iron  body  is  the  most  suit- 
able thing.     The  valve-seat,  valves,  spindles,  stuffing-box,  glands, 
and     nuts    are 
usually  made  of 
gun-m  e  t  a  1  or 
brass.  For  very 
high  pressures, 
especially      o  n 
steam  mains, 
cast  steel  is 
generally  used, 
with  gun-metal 
fittings  similar  to  those  enumerated  for  the  cast-iron  valves. 

Safety-Valves.  Safety-valves  are  used  for  reducing  the  pressure 
in  the  boiler  when  it  exceeds  a  certain  limit,  and  to  give  warning  of 
high  pressure.  There  are  several  different  types,  but  the  essential 
features  are  a  valve  opening  upward,  held  on  its  seat  by  a  weight  or 


Fig,  41.  Common  Type  of  Lever  Safety- Valvr 


181 


40  BOILER  ACCESSORIES 

spring.     When  the  pressure  in  the  boiler  exerts  a  force  greater  than 
that  holding  down  the  valve,  the  valve  will  open  automatically. 

The  lever  safety-valve  shown  in  Fig.  41  is  the  most  common  type 
for  stationary  work,  especially  for  small  boilers.  The  valve  is  held 
in  place  by  a  weight  at  the  end  of  a  lever.  The  force  required  to  lift 
the  valve  is  governed  by  the  location  of  the  weight  on  the  lever-arm. 

The.   body   of 


me    vaive     is 
!                                            j                         f-*5-j         usually   made 

I4L.  SOIbs.                                  c 

125  "") 

Fulcrum 

the  seat  being 
of  brass.     An 

Fig.  43.    Diagram  for  Safety-Valve  Calculations.  opening   C 

the  side  of  the 

valve  may  be  connected  with  the  feed-water  heater  or  drain,  if  the 
escape  of  steam  into  the  air  is  undesirable.  If  the  valve  becomes 
leaky,  it  should  be  reground;  but  no  attempt  should  be  made  to 
make  it  tight  by  increasing  or  moving  the  weight  on  the  lever. 

The  amount  of  necessary  weight  on  the  lever,  and  its  distance 
from  the  fulcrum,  can  be  determined  in  the  usual  manner  of  com- 
puting leverage  forces  and  moments,  remembering  that  weight 
times  weight-arm  is  equal  to  power  times  power-arm.  In  such  a 
valve  as  this,  power  is  the  steam  pressure,  and  the  power-arm  is  the 
distance  of  the  center  of  the  valve  from  the  fulcrum.  There  are  four 
weights  acting  downward — the  ball,  the  lever-arm,  the  valve,  and  the 
spindle — and  in  the  process  of  computation  the  weight  and  leverage 
of  each  must  be  taken  into  account. 

Suppose,  for  example,  that  we  have  a  lever  safety-valve  such  as 
is  illustrated  in  outline  in  Fig.  42,  and  that  we  know  the  following  con- 
ditions: the  ball  weighs  125  Ibs.,  and  is  suspended  at  the  end  of  the 
lever  48  inches  from  the  fulcrum ;  the  valve  and  valve  spindle  together 
weigh  18  Ibs.,  and  are  4^  inches  from  the  fulcrum;  the  lever-arm 
itself  weighs  50  Ibs.  If  the  valve-seat  is  5  inches  in  diameter,  at  what 
pressure  will  the  valve  blow  off,  ignoring  the  friction  of  the  stuffing- 
box  and  fulcrum  pivot? 

The  center  of  gravity  of  the  lever-arm  must  be  determined  from 
the  drawing  (Fig.  42),  and  this  is  found  to  be  20  inches  from  the 


182 


BOILER  ACCESSORIES 


4] 


fulcrum      The  leverage  of  the  weights  acting  downwards  is  then  as 
follows : 

Ball 125  X  48     =-•  6,000 

Lever 50x20    =1,000 

Valve  and  Stem 18  X    4£  =  _J_81 

Total  moment =  7,081  inch-pounds. 


Now,  if  the  valve-seat  diameter  is  5  inches,  the  area  of  the  valve 


will  be 


TT  D2       3.1416  X  25 


=  19.63  sq.  in.     The  total  moment  to 


4  4 

be  overcome  is  7,081  inch-pounds,  and  its  distance  from  the  fulcrum 
is  4-V  inches.     Therefore  the  necessary 
upward  pressure  on  the  valve   will  be 

Ibs.      If  the  area  of 


7,081       ,  r-Q  ~ 
-^==1,573.5 

the  valve  is    19.63  sq.    in.,    then    the 
necessary   pressure   in  pounds  per 

1  573  5 
square  inch  would  be    '"* 


19  . 


80  Ibs., 


approximately.  That  is,  this  safety- 
valve  would  blow  off  when  the  boiler 
pressure  reached  80  Ibs.  per  square  inch. 
If  it  is  desired  to  design  a  valve 
that  will  blow  off  at  known  pressure, 
the  same  principles  will  apply,  but  the 
computations  will  be  figured  in  the  re- 
verse order.  The  area  of  the  valve, 
times  the  boiler  pressure,  would  give 
the  total  lifting  force  ;  and  this,  multi- 
plied by  its  leverage,  would  give  the 
lifting  moment,  which  would  be  re- 
sisted by  the  downward  moment  of  the 
combined  weights  of  valve,  valve-stem, 
lever,  and  ball.  If  the  moments  of  the  lever,  valve,  and  valve-stem 
were  known,  the  rest,  of  course,  would  be  made  up  by  the  ball. 
If  the  length  of  the  lever-arm  were  known,  then  the  weight  of  the  ball 
would  be  varied  to  correspond;  and,  conversely,  if  the  weight  of  the 
ball  were  fixed,  the  length  of  the  lever  must  be  made  to  correspond. 


Fig.  43.    "Crosby"  Pop  Safety-Valve 
for  Stationary  Boilers. 


183 


BOILER  ACCESSORIES 


The  lever  safety-valve  has  several  defects.  It  does  not 
promptly  when  the  pressure  is  reduced ;  and  it  is  likely  to  leak  after 
it  is  closed,  and  may  readily  be  overloaded,  or  even  wedged  on  its 
seat.  It  is  essential  that  a  safety-valve  should  be  automatic,  certain 
in  its  action,  and  prompt  in  opening  and  closing  at  the  required 
pressure.  It  must  be  one  that  can  be  relied  upon  under  all  circum- 
stances. 

The  pop  safety-valve  fulfils  the  above  requirements  better  than 
those  of  the  lever  type.     Pop  valves  open  when  the  steam  pressure 

is  sufficient  to  overcome 
the  tension  of  the  spring. 
Fig.  43  shows  a  "Crosby" 
pop  safety-valve  for  sta- 
tionary service.  The 
valve  C  is  connected  by 
the  flange  B  to  .  the  cen- 
tral spindle  A,  and  is  held 
down  on  its  seat  by  the 
pressure  of  the  spring  S. 
The  valve  C  is  provided 
with  wing  guides  and  an 
annular  lip  E.  The 
guides  fit  smoothly  into 
the  seating  D,  upon 
which  the  valve  rests. 
The  seats  of  the  valve 
have  an  angle  of  45  de- 
grees. The  under  face  of  the  lip  E,  together  with  the  seating, 
forms  a  small  chamber  through  which  all  the  steam  must  paso 
to  the  open  air.  A  number  of  small  holes  drilled  vertically  through 
the  flange  F,  connect  with  the  chamber  and  allow  part  of  the 
steam  to  escape.  The  action  of  the  valve  is  regulated  by  the  screw 
ring  G,  which  allows  more  or  less  steam  to  escape  through  the  holes  in 
the  flange  F,  Raising  the  screw  diminishes,  and  lowering  it  increases, 
the  area  of  the  holes.  If  the  loss  of  steam  is  too  great  wrhen  the 
valve  blows,  turn  the  screw  ring  down. 

Safety-valves  should  be  connected  directly  to  the  boiler  without  any 
pipe  or  elbow.    They  should  be  tried  every  day  by  means  of  the  lever. 


Fig.  44.    "Ashton"  Valve  with  Pop  Regulator  for 
Stationary  Boilers. 


184 


BOILER  ACCESSORIES 


43 


The  valve  shown  in  Fig.  44  for  stationary  boilers,  is  made  by  the 
Ashton  Valve  Company.  The  general  principles  are  those  of  all  pop 
safety-valves.  The  valve-seat  is  made  of  composition  or  nickel,  and 
with  a  bevel  of  45  degrees,  as  is  the  United  States  Government  stand- 
ard. The  pop  chamber  is  surrounded  by  a  knife-edge  lip,  which 
wears  down  in  proportion  with  the  seat,  thus  keeping  the  outlet  of  the 
same  relative  proportions,  giving  a  constant  amount  of  pop. 

The  amount  of  pop — that  is,  the  difference  of  pressure  between 
the  opening  and  the  closing  of  the  valve — is  regulated  from  the  out- 


Fig.  45.    "Star  Marine"  Pop  Safety- Valve, 
wittrCam  Lever. 


Fig.  46.  "Ashton"  Safety-Valve  for 
Locomotive  Boilers,  with  Pop  Regula- 
tors on  Each  Side,  and  Top  Muffler. 


side  by  means  of  the  screw-plug  pop  regulator  shown  at  H  in  Fig.  44. 
If  more  pop  is  desired,  turn  the  regulator  so  that  S  will  be  more  nearly 
perpendicular.  To  lessen  pop,  make  0  more  nearly  perpendicular. 
The  springs  are  made  of  Jessop's  best  steel. 

The  inlet  and  outlet  are  both  on  the  same  casting,  so  that  the 
valve  may  be  taken  apart  to  be  cleaned  or  repaired,  without  disturbing 
the  boiler  connection.  It  has  a  lock-up  attachment,  so  that  the  regu- 
lating parts  cannot  be  tampered  \vith,  either  by  accident  or  by  design. 
The  spring  is  encased,  thus  protecting  it  from  the  steam. 


185 


44 


BOILER  ACCESSORIES 


The  "Star  Marine"  pop  safety-valve  is  shown  in  Fig.  45.  It 
has  a  bevel  seat,  and  is  provided  with  a  cam  lever  by  which  it  may  be 
raised  from  its  seat  when  there  is  no  steam  pressure.  The  outlet  of 
the  valve,  if  desired,  may  be  piped  to  the  supply  tank  or  to  any  other 
point. 

Safety-valves  for  locomotive  boilers  must  be  made  of  heavy  material 
to  stand  the  severe  usage.  They  should  be  so  constructed  that  they 
will  not  cock  or  tilt.  The  "Ashton"  valve  shown  in  Fig.  46  is  con- 


Fig.  47.    "Holt"  Reducing  Valve  with  Diaphragm  Regulating  Pressure. 

strticted  so  that  the  amount  of  pop  can  be  regulated  by  merely  turning 
the  two  posts  marked  2  and  3  to  the  right  or  left.  The  noise  of  the 
steam  escaping  from  the  ordinary  safety-valve  is  disagreeable,  and  in 
some  States  the  law  requires  the  use  of  the  muffler  safety-valve.  The 
Ashton  valve  shown  in  Fig.  46  has  a  top  muffler. 

Reducing  Valves.  Sometimes  steam  is  desired  at  a  lower  pres- 
sure than  that  of  the  boiler.  For  instance,  a  small  low-pressure  engine 
may  be  run  by  steam  taken  from  the  same  boiler  that  supplies  a 
higher-pressure  engine.  This  reduction  is  accomplished  by  throttling 
the  steam  by  means  of  reducing  valves.  These  are  arranged  to  be 


186 


BOILER  ACCESSORIES  45 

operated  automatically  so  that  the  pressure  can  be  reduced  and  a 
constant  pressure  in  the  steam  pipes  maintained.  There  are  several 
forms  in  general  use. 

In  the  "Holt"  valve,  Fig.  47,  the  low-pressure  steam  acts  on  the 
lower  side  of  the  diaphragm;  and  the  weight,  which  may  be  set  so  as 
to  cause  the  desired  pressure,  acts  on  the  other.  The  movement  of 
this  diaphragm  causes  a  balanced  valve  to  move  to  or  from  its  seat. 
The  valve  opens  until  the  steam  pressure  equals  the  weight  above. 
The  pressure  in  the  main  steam  pipe  does  not  affect  the  movement 
of  the  valve.  It  depends  only  upon  the  pressure  on  the  two  sides  of 
the  diaphragm. 

Another  form,  the  "Mason,"  is  shown  in  Fig.  48.  A  spring,  which 
may  have  its  tension  altered  by  a  key,  takes  the  place  of  the  lever  and 
weight  in  the  Holt  valve.  When  the  pressure  in  the  low-pressure 
system  has  risen  to  the  required  point,  which  is  determined  by  the 
spring,  the  valve  closes,  and  no  more  steam  is  admitted  until  the 
pressure  falls  sufficiently  to  open  the  valve  again. 

In  another  form,  a  piston  acted  on  by  the  low-pressure  steam 
regulates  the  opening  of  a  balanced  valve,  and  this  maintains  a  con- 
stant steam  pressure. 

In  the  "Foster"  reducing  valve,  the  valve  is  held  open  by  the 
spring  and  levers,  until  the  steam  pressure  at  exit  presses  on  the  dia- 
phragm sufficiently  to  close  the  valve.  The  valve  is  held  open  so  as 
to  admit  just  the  proper  amount  of  steam  to  maintain  the  required 
pressure. 

When  a  reducing  valve  is  used,  a  stop-valve  should  be  put  in  to 
prevent  flow  when  steam  is  not  in  use. 

BLOW=OUT  APPARATUS 

Boiler  feed-water,  if  taken  from  rivers  or  ponds,  is  likely  to 
contain  vegetable  matter  as  \vell  as  solid  materials.  The  vegetable 
matter  will  usually  float  to  the  surface,  while  the  solids  will  collect  at 
the  bottom.  To  keep  the  boiler  clear  of  such  sediment,  it  is  neces- 
sary to  provide  two  blow-outs — a  surface  blow-out,  to  take  care  of 
what  rises  to  the  top;  and  a  bottom  blow-out,  to  take  out  the  sediment 
that  collects  at  the  bottom  of  the  boiler.  The  surface  blow-out 
usually  consists  of  a  dish  or  funnel-shaped  receptacle  set  with  its  face 


187 


BOILER  ACCESSORIES 


vertical,  as  shown  in  Fig.  49.  When  the  water-level  is  in  line  with 
this  blow-out  opening,  the  opening  of  the  valve  at  the  bottom  will 
skim  the  impurities  from  the  surface  of  the  water  quite  readily.  Oil 
may  get  into  the  boiler  through  the  feed- 
water,  and  a  considerable  portion  of  it 
can  be  removed  in  this  manner. 

The  bottom  blow-out  consists  merely 
of  a  pipe  leading  from  the  bottom  of  the 
boiler  outward.  Both  these  blow-outs 
may  be  connected  into  one  outlet. 

In  water-tube  boilers  a  mud-drum 
is  usually  installed,  which  readily  collects 
the  solid  matter,  and  the  bottom  blow- 
out is  then  connected  with  this  mud-drum. 
Fig.  50  shows  an  arrangement  of  surface 
and  bottom  blow-outs  as  usually  installed 
on  a  Scotch  boiler  of  the  marine  type. 

If  the  feed-water  contains  salt,  which 
may  frequently  happen  in  marine  prac- 
tice, it  is  necessary  that  the  boiler  should 
frequently  be  blown  out  in  order  to  re- 
move the  excess  of  salt.  The  density  of  the 
boiler  water,  if  salt  feed  is  used,  should  be  carefully  determined  by  a 
salimeter.  The  loss  due  to  this  frequent  blowing  oiit  is  considerable, 
as  a  large  amount  of 
heat  is  necessarily  wasted , 
but  it  cannot  be  avoided, 
except  by  the  use  of 
fresh  water,  which  some- 
times may  be  impossible 
at  sea. 

The  blow-out  pipe 
leading  from  the  bottom 
of  an  externally-fired 
boiler  through  the  brick 
setting,  if  not  properly 
protected,  may  be  burned  off,  owing  to  the  heat  of  the  fire.  This 
pipe  is  frequently  covered  with  asbestos  or  other  fire-resisting  material; 


Fig.  48.   "Mason"  Reducing  VaU 

Pressure  Regulated  by  Means 

of  a  Spring. 


Fig.  49.    Surface  Blow-Out  Installed  in  Boiler. 


188 


BOILER  ACCESSORIES 


47 


V 



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::;v;-:J2 

ice  Blow 

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V    a. 

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to    ^ 

tx 

£ 

V. 

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3  * 


II 


189 


4S 


BOILER  ACCESSORIES 


but  it  can  be  best  protected  by  the  means  shown  in  Fig.  51.  A  pipe 
connected  to  the  boiler  slightly  below  the  water-level,  runs  out  through 
the  brick  setting  and  connects  into  the  main  blow-out  pipe.  This 
causes  a  circulation  of  water  continually  to  pass  through  the  system, 
and  prevents  destruction  of  the  blow-out  pipe.  When  it  is  necessary 
to  use  the  bottom  blow-out,  the  valve  A  is  closed,  and  the  blow-off 
valve  B  is  opened;  otherwise,  B  is  closed,  and  A  is  open  while  the 
water  circulates. 

The  blo\v-out  pipe  is  usually  shut  off  by  a  cock,  which,  although 
not  so  easily  operated  as  a  valve,  is  more  trustworthy.  Frequently 
both  a  cock  and  a  valve  are  provided.  Should  a  small  particle  of 

sediment  lodge  on 
the  valve-seat,  it 
would  be  impossi- 
ble to  close  the 
valve  tightly,  and 
a  considerable  leak- 
age would  result, 
while  an  inspection 
of  the  valve  wrould 
not  indicate 
whether  it  were 
completely  closed 
or  not.  But  a 
glance  reveals  the  fact  whether  or  not  a  cock  is  tightly  closed.  The 
cock  is  likely  to  stick  because  of  corrosion  or  unequal  expansion, 


^AA/ater  Level 

Boner 

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J£ 
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Fig. 


Valve -A 


Valve -B' 

Method  of   Protecting  Bottom  Blow-Out  Pipe  by 
Means  of  Circulation  Pipe  Connected  to  Boiler. 


but,  if  frequently  opened,  this  difficulty  is  not  of  great  weight. 
The  plug  and  casing  of  the  cock  should  not  be  made  of  the  same 
material,  as  in  that  case  they  will  more  readily  stick  if  the  cock 
remains  closed  any  length  of  time. 

FEED  APPARATUS 

Perhaps  the  most  important  of  all  auxiliaries  connected  with  the 
boiler  is  the  feed  apparatus.  This  is  vital;  for,  if  the  feed  is  inter- 
rupted and  the  water  runs  low  in  the  boiler,  not  only  is  there  danger 
of  damaging  the  boiler  itself,  but  a  disaster  may  follow  of  far  greater 
concern.  For  marine  purposes — and  the  same  is  true  to  a  consider- 


190 


BOILER  ACCESSORIES  49 

able  extent  in  stationary  work — at  least  two  independent  feed  systems 
should  be  provided.  In  marine  work,  the  main  feed-pump  draws 
water  from  the  filter  box  or  feed-water  heater,  and  pumps  it  into  the 
boilers  under  ordinary  conditions.  There  should  be  a  by-pass  around 
this  pump,  and  the  feed  line  should  be  connected  by  means  of  a  valve 
to  what  is  known  as  the  donksy  pump,  which  may  be  used  for  auxiliary 
feed  purposes  in  case  the  main  pump  is  damaged  or  needs  repairs  in 
any  way. 

Both  these  pumps  draw  from  and  discharge  into  the  same  feed 
line;  but,  to  provide  against  emergencies,  there  is  usually  a  cross- 
connection  to  the  sea,  so  that  sea  water  may  be  had  if  necessary. 
While  in  port,  when  the  main  engines  are  not  running,  and  conse- 
quently when  the  feed-water  cannot  be  heated  economically,  an  in- 
jector is  almost  invariably  used.  On  land  it  is  usually  considered 
sufficient  to  install  an  injector  in  addition  to  the  feed  pump,  although 
in  large  plants  an  auxiliary  feed  pump  should  be  installed  as  well.  In 
a  small  plant  the  fireman  usually  attends  to  the  water;  but  on  board 
ship  and  in  large  plants,  a  water  tender  is  usually  provided,  whose 
business  it  is  to  keep  the  water  in  the  boiler  at  the  proper  level.  His 
task  may  be  materially  lessened  by  some  automatic  arrangement,  so 
that  if  the  water  discharged  into  the  hot  well  from  the  condenser  rises 
fcibove  the  normal  level,  a  float  will  open  the  valve  leading  to  the  feed- 
pump and  increase  the  rapidity  of  its  stroke.  This  will  reduce  the 
level  of  the  hot  well  or  filter  box,  as  the  case  may  be. 

Such  an  arrangement  as  this  will  keep  a  fairly  uniform  level  of 
water  in  the  boilers;  and  if  a  surface  condenser  is  employed,  and  all 
the  condensation  is  pumped  back  into  the  boilers,  the  water-level  will 
remain  constant  except  for  slight  leakages  of  steam  and  for  the  possi- 
bility of  improper  action  of  the  feed-pump.  Leakage  of  steam  can 
be  made  up  from  the  supply  of  fresh  water.  At  sea,  salt  water  may  have 
to  be  used  for  this  purpose  although  its  use  is  objectionable. 

There  is  a  considerable  difference  of  opinion  as  to  where  the  feed- 
water  should  be  introduced  into  the  boiler,  although  the  consensus 
of  opinion  seems  to  be  that  it  should  enter  not  far  from  the  water-line. 
In  stationary  practice,  the  feed-water  is  introduced  at  the  rear  of  the 
boiler  near  the  bottom;  but  this  is  open  to  grave  objections,  for  the 
feed-water,  being  comparatively  cool  and  being  introduced  into  the 
coldest  part  of  the  boiler,  naturally  tends  to  become  dead  water  and  to 


191 


50  BOILER  ACCESSORIES 

retard  proper  circulation  which  is  essential  to  economical  steaming 
and  often  essential  to  the  safety  of  the  boiler  itself. 

The  best  place  for  introducing  the  feed-water  will  naturally 
depend  upon  the  type  of  boiler,  and  the  service  for  which  it  is  intended. 
If  the  entering  water  is  of  high  temperature,  it  might  enter  near  the 
bottom  of  the  boiler.  But  if  the  feed-water  is  comparatively  cold  — 
and  it  is  always  colder  than  the  water  in  the  boiler  and  the  surround- 
ing steam  if  the  circulation  is  good — great  care  must  be  taken  that 
it  does  not  strike  directly  against  the  hot  boiler-plates,  as  it  might 
thereby  cause  local  contraction  and  possibly  a  serious  leak,  and  it 
should  be  introduced  in  such  a  way  as  to  make  sure  of  its  aiding  the 
natural  circulation  of  the  boiler. 

The  higher  the  steam  pressure  in  the  boiler,  the  more  difficult 
becomes  the  problem  of  feed,  and  the  more  danger  there  is  of  injury 
to  the  boiler  by  the  comparatively  cold  feed-water  striking  hot  plates. 
It  is  a  universal  practice  in  marine  work,  and  a  common  practice  on 
land,  especially  for  internally-fired  boilers,  to  cause  the  feed  to  enter 
above  the  water-level  near  the  center  of  the  boiler;  then  branching 
off  into  two  pipes,  one  leading  to  each  side  through  the  steam  space 
until  the  side  of  the  boiler  is  reached;  and  then  running  downward 
toward  the  bottom.  The  feed-water,  which  very  likely  has  been 
previously  heated  by  a  feed-water  heater,  is  still  further  heated  by  its 
passage  through  this  feed-pipe,  which  is  in  direct  contact  with  the  live 
steam  of  the  boiler.  This  internal  feed-pipe,  turning  down  at  the  sides, 
causes  the  water  to  strike  the  outer  shell  of  the  boiler  which  is  the 
most  remote  from  the  fire,  and  this  downward  motion  materially 
assists  the  circulation  in  the  boiler.  When  this  arrangement  of  feed 
is  adopted  (see  Fig.  50),  care  must  be  taken  that  the  lower  end  of 
the  feed-pipe  is  well  below  the  low-water  level.  If  the  end  of  the 
pipe  is  alternately  immersed  in  water  and  then  exposed  to  steam, 
violent  explosions  in  the  pipe  are' likely  to  follow,  although  they  are 
likely  to  do  nothing  more  serious  than  break  an  elbow  or  frighten 
the  attendants. 

In  stationary  practice,  it  is  quite  common  to  admit  the  feed-water 
into  the  steam  space  through  a  horizontal  pipe  entering  it  through  the 
tube-plate  a  few  inches  below  the  low-water  level,  and  terminating  in 
a  perforated  pipe  of  large  diameter.  This  method  distributes  the  feed- 
water  admirably,  and  allows  it  to  become  considerably  heated  before 


192 


BOILER  ACCESSORIES 


51 


it  reaches  the  bottom  of  the  boiler.  If  the  feed-water  contains  a  con- 
siderable amount  of  magnesia  or  calcium  carbonate,  holes  so  arranged 
in  the  feed-pipe  are  likely  to  become  clogged  and  the  feed  interrupted. 
Water  of  this  sort  should  be  fed  into  a  trough,  or  the  feed-pipe  be 
opened  at  the  top  by  a  long  slot,  so  that  the  feed-water  may  over- 
flow. The  trough  in  this  case  forms  an  admirable  mud-drum  or 
sediment  collector. 

In  internally-fired  boilers  of  the  "Cornish"  or  "Lancashire"  type, 


Steam-Driven  Boiler  Feed-Pump. 


the  feed  is  usually  delivered  near  the  bottom  through  a  horizontal 
pipe — either  through  the  front  end  or  by  a  vertical  pipe  through  the 
crown.  This  msthod  is  not  conducive  to  the  best  circulation. 

In  addition  to  these  effects  on  circulation,  there  are  other  grave 
objections  to  introducing  feed -water  near  the  bottom  of  the  boiler;  for, 
should  anything  happen  to  the  feed-pump,  or  a  piece  of  scale  lodge 
under  the  check-valve,  the  water  might  be  almost  entirely  blown  out 
of  the  boiler  before  the  difficulty  could  be  discovered  or  remedied. 


193 


52 


BOILER  ACCESSORIES 


If  the  pipe  enters  in  the  vicinity  of  the  low-water  level,  no  water  could 
be  drawn  out  below  this  point. 

The  feed  supply  should  always  be  regulated  so  as  to  keep  the 
water-level  as  nearly  stationary  as  possible;  this  is  not  only  much 
more  economical,  but  also  far  better  for  the  boiler,  than  to  wait  for  the 
water-level  to  fall  and  then  feed  a  few  inches  rapidly.  The  sudden 
introduction  of  a  large  volume  of  comparatively  cold  feed-water,  causes 
local  contraction  of  the  plates,  and  hence  tends  to  cause  leakage; 


Fig.  53.    Section  or  "Worthington"  Duplex  Steam  Pump. 

moreover,  it  necessitates  irregular  firing  if  anything  like  a  uniform 
steam  pressure  is  to  be  maintained. 

Sometimes  the  feed-water  is  forced  into  the  steam  space  in  the 
form  of  a  fine  spray.  In  this  way  it  not  only  is  thoroughly  heated 
before  mingling  with  the  water  in  the  boiler,  but  the  air  is  got  rid  of; 
and  salts,  such  as  sulphate  of  lime,  insoluble  at  high  temperatures, 
are  immediately  precipitated.  But  the  advantage  of  introducing  the 
feed-water  in  a  body  so  as  to  produce  useful  circulating  currents, 
should  not  be  overlooked, 


194 


BOILER  ACCESSORIES  53 

If  several  boilers  are  attached  together  in  the  form  of  a  battery, 
each  should  be  supplied  with  an  independent  connection  to  feed- 
pipe. Otherwise  a  damage  to  the  feed-pipe  in  one  boiler  might  aft'ect 
the  others.  Moreover,  if  several  boilers  are  fed  from  one  pipe,  the 
pressure  in  each  of  them  being  slightly  different,  an  excess  of  water 
will  naturally  be  fed  into  the  boiler  having  the  least  pressure,  whereas 
it  is  usually  the  case  that  the  most  water  is  needed  in  the  boiler  hav- 
ing the  greatest  pressure.  The  automatic  float  previously  referred  to, 
can  regulate  the  amount  of  water  fed  into  boilers  only  in  a  general 
way,  through  providing  a  method  by  means  of  which  all  the  con- 
densation is  fed  back  into  some  of  the  boilers;  but  the  quantity  of 
feed  which  is  led  into  each  individual  boiler  must  be  watched  and 
regulated  by  the  water  tender,  who  can  open  or  close  the  individual 
valves  as  desired. 

Pumps.  Boilers  are  usually  fed  by  a  small,  direct-acting 
steam  pump  placed  near  the  boiler.  Although  these  pumps  require 
a  large  steam  supply  per  horse-power  per  hour,  the  total  amount  of 
steam  used  is  small  because  the  work  done  is  small  A  more  eco- 
nomical pump  is  the  power  pump  driven  by  the  large  steam  engine; 
but  in  this  case  the  rate  at  which  water  is  supplied  is  not  easily  regu- 
lated to  the  demand  of  the  boiler.  Power  pumps  are  usually 
arranged  to  pump  a  larger  quantity  of  water  into  the  boiler  than  is 
required,  the  excess  of  water  being  allowed  to  flow  back  into  the 
suction  pipe  through  a  relief  valve. 

The  pump  shown  in  Fig.  52  is  well  adapted  for  feeding  boilers. 
In  Fig.  53  is  shown  the  section  of  a  duplex  "Worthington"  steam  pump. 
The  action  of  each  of,  these  two  types  is  similar.  Steam,  controlled 
by  valves,  drives  the  piston  in  the  steam  cylinder,  which  moves  the 
plunger  in  the  water  cylinder,  since  both  are  fastened  to  the  same  rod. 
The  movement  of  the  plunger  forces  a  part  of  the  water  in  front 
of  it  up  through  the  valves  into  the  air-chamber,  and  through  the 
pipes  into  the  boiler.  On  account  of  the  partial  vacuum  caused  by  the 
movement  of  the  plunger,  water  will  be  drawn  from  the  suction  pipe, 
through  the  valves,  into  the  pump  cylinder,  filling  the  space  left  by 
the  movement  of  the  plunger.  During  the  return  stroke,  this  water 
is  forced  up  into  the  air-chamber,  and  a  like  quantity  enters  the  other 
end  of  the  pump  cylinder.  The  valves  are  kept  on  the  seats  by  light 


195 


BOILER  ACCESSORIES 


STEAM 


springs,  until  the  pressure  on  the  bottom  side  is  sufficient  to  lift  them 
and  allow  water  to  flow  through. 

When  two  pumps  are  placed  side  by  side,  and  have  a  common 
delivery  pipe,  the  machine  is  called  a  duplex  pump.     It  is  usual  to  set 

the  steam  valves  so  that 
when  one  piston  is  at  the 
end,  the  other  is  at  the  mid- 
dle of  its  stroke.  A  duplex 
pump  having  a  large  air- 
chamber  and  valves  set  to 
act  in  this  manner,  delivers 
water  w  i  t  h  an  approxi- 
mately constant  velocity. 

Injectors.  Water  may  be 
forced  into  a  boiler  by  an 
injector  or  inspirator.  By 
means  of  this  instrument, 
the  energy  of  a  jet  of  steam 
is  used  to  force  the  water 
into  the  boiler.  That  there 
is  sufficient  energy  to  do 
this  work  is  evident  from 
the  fact  that  each  pound  of 
steam,  in  condensing,  gives 
up  about  1,000  B.  T.  U., 
and  a  B.  T.  U.  is  equiva- 
lent to  778  foot-pounds. 
Not  all  the  energy  of  the  jet 
of  steam  is  used  in  forcing 
water  into  the  boiler;  some 
is  wasted,  and  much  is  used 
to  heat  the  feed-water. 

The  action  of  the  injector 
is  briefly  as  follows:  The  steam  escapes  from  the  boiler  with 
great  velocity,  and,  as  it  passes  through  the  cone-shaped  passage, 
draws  air  along  with  it,  thus  creating  a  partial  vacuum  in 
the  suction  pipe.  Atmospheric  pressure  forces  water  up  into  the 
suction  pipe,  and  the  jet  of  steam  which  it  meets  is  partly  condensed. 


OVERFLOW 

Fig.  51.    Sectional  View  of  "Hancock"  Injector. 


196 


BOILER  ACCESSORIES 


55 


The  energy  of  the  jet  carries  the  water  along  with  it  into  the  boiler. 

Experiments  show  that  the  injector,  if  considered  as  a  pump, 
has  a  very  low  efficiency.  When  used  for  feeding  a  boiler,  it  has  a 
thermal  efficiency  of  nearly  100  per  cent,  since  all  the  heat  of  the  steam 
passes  to  the  water  except  STEAM 
the  slight  amount  lost  in 
radiation.  The  pump, 
however,  has  one  great  ad- 
vantage over  the  injector; 
it  can  force  hot  water 
/rom  a  heater  into  the 
boiler,  while  an  injector 
can  be  used  only  with  cold 
or  moderately  warm  water. 

Figs.  54  and  55  show 
the  interior  section  and 
exterior  of  a  "Hancock" 
inspirator.  To  inject  water 
to  the  boiler,  first  open 
overflow  valves  1  and  3; 
close  valve  2;  and  open 
starting  valve  in  the  steam 
pipe.  When  the  water  ap- 
pears at  the  overflow, 
open  2  one  quarter-turn, 
close  1,  and  then  close  3. 
The  inspirator  will  then  be 
in  operation.  When  the 
inspirator  is  not  working, 
open  both  1  and  3  to  allow 
water  to  drain  from  it. 

Both  temperature  and 
quantity  of  delivery,  water 
can  be  varied  by  increas- 
ing or  decreasing  the  water  supply.  When  the  water  in  the  suction 
pipe  is  hot,  either  cool  off  both  pipe  and  injector  with  cold  water, 
or  pump  out  the  hot  water  by  opening  and  closing  the  starting  valve 
suddenly. 


OVERFLOW 

Fig.  55.    Exterior  View  of  "Hancock"  Injector. 


197 


56  BOILER  ACCESSORIES 

Circulating  Apparatus.  There  is  always  more  or  less  danger  in 
starting  a  fire  under  a  boiler.  If  the  circulation  is  poor,  the  result 
will  be  that  not  only  will  the  water  be  of  an  uneven  temperature,  hot 
near  the  top  and  cold  at  the  bottom,  but  the  boiler  shell  is  likely  to 
be  subjected  to  severe  strain,  owing  to  the  difference  of  temperature 
arising  from  the  stagnation  of  the  cold  water  near  the  bottom.  The 
fire  must  be  started  slowly,  and  a  considerable  time  consumed  in 
getting  up  steam.  To  overcome  the  difficulty  of  poor  circulation, 
several  mechanical  devices  have  been  applied. 

The  first  device  tried  was  a  hydro-kinder — a  sort  of  injector — in 
which  jets  of  steam  driven  through  a  conical  nozzle  drew  in  the  sur- 
rounding water.  This  was  so  arranged  as  to  induce  the  cold  water 
to  flow  from  the  bottom  toward  the  top,  where  it  was  more  intensely 
heated.  This  arrangement  is  efficient,  but  slow  of  action.  In  large 
marine  boilers — in  which  the  fire  is  cautiously  started,  as  is  proper — 
the  temperature  at  the  surface  of  the  water,  four  hours  after  lighting 
up,  has  been  found  to  be  as  high  as  205°,  while  at  the  bottom  it  was 
only  73°.  Several  observations  with  a  hydro-kineter  in  action  have 
shown  the  temperatures  to  be  205°  and  144°  respectively.  It  was 
six  hours  more  before  the  temperature  was  equalized  throughout. 

In  naval  vessels,  where  it  is  frequently  necessary  to  raise  steam 
rapidly,  this  device  is  altogether  too  slow.  It  has,  moreover,  two 
other  drawbacks.  There  must  be  an  auxiliary  boiler  under  steam 
pressure,  and  it  will  cease  to  act  when  the  temperature  and  pressure 
of  steam  in  the  main  boiler  has  reached  that  in  the  auxiliary  boiler. 
The  steam  jet,  in  the  American  Navy,  has  been  replaced  by  a  jet  of 
feed-water  forced  through  a  conical  nozzle.  This  arrangement 
answers  very  well  so  long  as  steam  is  being  drawn  from  the 
boiler;  but  when  the  boiler  is  at  rest  and  steam  is  being  raised,  it  is 
inoperative. 

The  best  service  can  be  had  by  means  of  small  centrifugal  pumps 
fixed  beside  the  boilers,  which  take  water  from  the  bottom  of  the 
boilers  and  discharge  it  a  little  below  the  water-level.  The  pumps 
may  be  turned  by  hand  while  raising  pressure,  and  may  be  worked 
by  steam  when  sufficient  pressure  has  been  attained.  A  small  engine 
of  perhaps  \\  horse-power  is  sufficient  to  give  a  proper  circulation  to 
a  large  boiler.  With  such  a  circulating  device,  steam  can  be  raised 
with  safety,  in  a  comparatively  short  time. 


198 


BOILER  ACCESSORIES 


57 


Evaporators.  No  engine  can  be  run  without  a  certain  loss  of 
water,  due  either  to  a  slight  continuous  leakage  or  to  blowing  off.  In 
stationary  practice,  this  loss  can  be  readily  made  up  by  the  appli- 
cation of  fresh  water;  but  at  sea  it  is  seldom  possible  to  carry  a  suffi- 
cient amount  of  fresh  water,  and  the  make-up  must  be  had  either 
from  sea  water,  or  from  fresh  water  provided  by  the  use  of  an  evapora- 
tor. The  evaporator  is  really  a  small  boiler,  the  water  in  which  is 


EXHAUST  OUTLET 


Scu.rnBlow 
Water  Line 


Fig.  56.    Peed-Water  Heater, 
Closed  Type. 


Fig.  57.    Feed-Water  Heater, 
Opeu  Type. 


heated  by  a  steam  coil  supplied  from  the  main  boiler.  The  evaporated 
water — called  the  evaporation — passes  into  the  condenser  and  then 
becomes  a  part  of  the  regular  feed  water. 

In  a  single  evaporator,  if  the  evaporation  passes  directly  to  the 
condenser,  its  heat  is  lost  to  useful  work.  To  provide  a  more  econom- 
ical arrangement,  multiple  evaporators  are  installed,  which  consist  of 
a  series,  the  evaporation  from  the  first  passing  into  a  coil  in  the  bottom 
of  the  second;  the  water  in  the  second  condenses  the  evaporation 
from  the  first,  while  at  the  same  time  the  evaporation  from  the  first 


199 


58 


BOILER  ACCESSORIES 


helps  to  heat  the  water  of  the  second.     The  steam  and  water  pass 
through  the  series  of  heaters  in  opposite  directions. 

It  is  a  rule  in  the  French  Navy,  to  provide  380  Ibs.  of  fresh  water 

per  hour  for  each 

LExhaust  Outlet 


Regulating 
'alve 


OilSeparat 


Ex.  Wet 
SkimmeT" 


1,000  indicated 
horse-power;  this 
provides  for  a  loss 

Cold  Water  of  about  2  Per  cent 
Supply          without,    drawing 

on  the  reserve  sup- 
ply, which  is  4,500 
Ibs.  for  the  same 
amount  of  power. 
The  evaporator 
may  be  arranged 
to  communicate 
with  a  low-pres- 
sure valve-chest, 
in  which  case  the 
evaporation  may 
be  made  to  do 
work  in  a  low- 
pressure  cylinder 
of  a  triple-expan- 
sion engine  before 
entering  the  con- 
denser, or  it  may 
be  connected  with 
the  feed-water 
heater  if  the  ex- 
haust steam  is  in- 
adequate. 

Feed  =  Water 
Heaters.  The  in- 
troduction of  feed- 
water  at  a  high 
temperature  increases  the  economy  and  tends  to  prolong  the  life  of 
the  boiler.  The  injurious  effects  from  unequal  expansion  are  dimin- 


Oil  Separate' 


Fig.  58.    "Cochrane"  Combined  Feed-Water  Heater  and 
Puriner,  Open-Heater  Type. 


300 


BOILER  ACCESSORIES 


ished ;  and  when  the  feed  is  warmed  by  exhaust  steam  or  by  the  waste 
gases  in  the  uptake,  the  saving  of  fuel  is  considerable. 

If  this  gain  comes  from  waste  gases  or  exhaust  steam,  which 
would  otherwise  make  no  return  for  their  heat,  the  gain  is  clear;  but 
there  is  no  gain  in  thermal  economy  by  heating  feed-water  with  live 
steam  directly  from  the  boiler. 

There  are  several  ways  of  heating  the  feed-water.  In  condensing 
engines,  the  feed-pump  discharges  from  the  condenser  into  the  hot 
well,  and  the  water  is  drawn  from  the  hot  \vell  at  a  temperature  of 
100°  to  140°  F.  This,  however,  if  the  pressure  is  over  100  Ibs.,  is 
entirely  inadequate;  and  for  the  best  economy,  feed-water  at  this 
temperature  should  be  passed  through  some  form  of  feed-water 
heater.  In  the  non-condensing  engines,  it  is  absolutely  necessary 
that  in  some  way  the  feed-water  should  be  heated  by  the  exhaust 
steam  or  by  waste  gases  from  the  chimney,  the  apparatus  in  the  first 
case  being  called  a  feed-water  heater,  and  in  the  second  an  economizer. 

The  feed-water  heater  may  be  arranged  so  that  it  will  not  only 
heat  the  water,  but  will  at  the  same  time  purify  it,  precipitating  the 
calcium  and  magnesia  salts,  which  collect  on  suitably  prepared  plates, 
and  gathering,  at  the  bottom  of  the  heater,  dirt  and  other  sediment 
that  would  injure  the  boiler. 

There  are  two  types  of  feed-water  hrater — the  open,  which  is 
frequently  used  in  land  work;  and  the  closed,  which  may  be  used 
either  on  land  or  at  sea.  In  the  open  heater,  the  steam  raises  the 
temperature  of  the  water  by  mingling  with  it  in  direct  contact.  The 
closed  type  of  heater  resembles  in  its  action  a  surface  condenser;  the 
steam  used  for  heating  purposes  surrounds  tubes  which  contain  the 
feed -water,  or  the  water  circulates  about  tubes  through  which  the 
heating  steam  passes. 

Fig.  56  shows  a  feed-water  heater  of  the  closed  type,  the  exhaust 
steam  heating  the  feed-water  within  the  tubes.  The  heater  shown  in 
Fig.  57  is  of  the  open  type,  the  feed-water  becoming  heated  and  depos- 
iting sediment  while  flowing  from  one  tray  to  another. 

The  "Cochrane"  heater,  Fig.  58,  is  a  combined  heater  and  puri- 
fier of  the  open-heater  type,  the  water  entering  at  the  top  and  flowing 
in  a  thin  sheet  over  a  series  of  trays.  The  exhaust  steam  enters 
through  the  oil  separator,  and  rising  among  the  trays,  heats  the  water 
to  about  210°  F,  the  action  being  similar  to  that  of  a  jet  condenser. 


201 


60  BOILER  ACCESSORIES 

The  gases  held  in  solution  in  the  feed-water  are  liberated  by  the  heat, 
and  escape  into  the  atmosphere ;  while  the  mineral  impurities  in  solu- 
tion, which  cause  scale,  are  precipitated  by  the  heat,  and  are  deposited 
on  the  trays  instead  of  on  the  plates  and  tubes  of  the  boiler.  The 
impurities,  mud,  clay,  etc.,  settle  to  the  bottom,  because  of  the  large 
surface  and  consequent  low  velocity  of  the  feed-water  through  the 
heater,  and  are  readily  removed.  Coke,  hay,  etc.,  are  used  for  filters, 
a  strainer  being  constructed  so  that  the  hay  or  coke  will  not  enter 
the  pump.  The  impurities,  having  less  specific  gravity  than  the 
water,  collect  at  the  surface,  and  are  removed  by  flushing. 


BOILER  ACCESSORIES 

PART  II 


STEAM  SEPARATORS 

Priming.  Steam  is  said  to  be  wet  or  to  be  superheated,  according 
as  it  has  an  excess  of  moisture  or  an  excess  of  heat.  Wet  steam  not 
only  is  uneconomical,  because  it  carries  a  considerable  amount  of  heat 
into  the  engine  in  the  form  of  water,  which  cannot  do  useful  work, 
but,  if  a  considerable  amount  of  water  gets  into  the  engine,  it  is  really 
dangerous,  for  it  may  so  completely  fill  the  clearances  that  the  piston 
will  strike  a  blow  against  the  cylinder-head  sufficient  to  break  it.  The 
water  in  the  pipes,  moreover,  may  cause  a  serious  hammering,  which 
lot  only  is  exceedingly  annoying,  but  may  be  actually  dangerous,  for  a 
severe  water-hammer  may  break  the  joints  of  the  steam  pipes,  and  a 
considerable  quantity  of  escaping  steam  at  high  pressure  would  be 
exceedingly  dangerous  to  the  lives  of  the  engine-room  attendants. 
This  especially  would  be  true  on  board  ship,  where  the  engine-room  is 
small,  the  supply  of  air  meager,  and  the  means  of  escape  limited. 

A  considerable  amount  of  water  may  be  deposited  in  a  sag  in  the 
pipe  line,  and  would  undoubtedly  remain  there  for  a  considerable 
length  of  time  if  the  pressure  in  the  boiler  did  not  fluctuate;  but  a 
sudden  rise  of  boiler  pressure  would  likely  cause  this  water  to  pass 
bodily  through  the  pipe  toward  the  engine.  Moisture  is  carried 
directly  from  the  boiler  as  a  result  of  priming.  This  is  caused  by 
steam  bubbles  which,  instead  of  bursting,  become  connected  on  the 
surface  of  the  water,  forming  a  foam,  half-liquid,  half-gaseous,  which 
fills  the  steam  space  and  passes  out  of  the  steam  pipe.  Priming  may 
be  due  to  fluctuations  of  boiler  pressure  or  to  the  presence  of  dirt,  oil, 
or  other  foreign  matter.  The  smaller  the  free  surface  of  the  water 
in  the  boiler,  the  more  likely  the  water  is  to  prime.  Boilers  will  fre- 
quently prime  badly  under  forced  draft,  when  otherwise  there  would 
be  little  trouble. 

Priming  may  be  detected  from  the  unusual  behavior  of  the  water 
in  the  gauge-glass,  or  from  the  hammering  in  the  steam  pipes  cr 


203 


62 


BOILER  ACCESSORIES 


cylinder.  To  avoid  a  breakdown  under  such  conditions,  the  speed  of 
the  engine  should  be  reduced,  the  drain-cocks  of  the  cylinders  and 
pipes  opened,  and  the  fires  eased  down.  Sometimes,  by  suddenly 
shutting  the  main  stop-valve,  the  pressure  in  the  boiler  can  be  in- 
creased sufficiently  to  overcome  the  difficulty. 

Almost  any  boiler  is  likely  to  prime  to  some  extent;  and  to  obtain 
as  dry  steam  as  possible,  several  devices  are  employed.  On  the  top 
of  stationary  boilers  and  locomotives,  a 
steam  dome  is  frequently  built,  from 
which  the  steam  is  drawn,  the  idea  being 
that  less  moisture  will  be  found  here  than 
if  the  steam  be  drawn  directly  from  tl»e 
main  portion  of  the  boiler.  In  marine 
work,  and  sometimes  in  stationary  plants, 
a  dry-pipe  is  used  (see  Fig.  50).  This  is 
merely  a  large  pipe  inside  the  boiler,  from 
which  the  steam  is  drawn.  The  pipe  is 
near  the  top  of  the  boiler,  and  the  upper 
side  of  it  is  perforated  with  holes  through 
which  the  steam  may  pass.  A  consider- 
able amount  of  moisture  is  in  this  way 
prevented  from  leaving  the  boiler. 

The  moisture  in  steam  can  be  reduced 
by  the  familiar  process  of  superheating; 
but  if  this,  for  any  reason,  is  impractica- 
ble or  undesirable,  a  steam  separator  may 
be  used  for  the  purpose  of  extracting  the 
moisture  that  comes  from  the  priming  of 
the  boiler  or  from  condensation  in  the 
steam  pipe. 

Separators.  There  are  several  forms  of  separator;  but  all  are 
designed  on  the  general  principle  that  if  the  direction  of  the  steam 
current  is  suddenly  changed,  or  if  it  is  diverted  upward  and  then  down- 
ward, the  water  will  be  separated  from  the  steam  and  will  fall  to  the 
bottom  of  a  suitable  receptacle.  The  depth  of  water  collected  in  the 
bottom  of  the  separator  is  readily  indicated  by  a  gauge-glass,  and  it 
may  be  drawn  off  as  desired.  To  prevent  the  possibility  of  flooding 
the  separator,  it  is  well  to  connect  it  with  an  automatic  trap  which 


Fig.  59.    "Stratum"  Separator. 


804 


BOILER  ACCESSORIES 


63 


will  empty  it  without  close  attention  from  the  engineer.  It  is  needless, 
of  course,  to  say  that  the  trap  from  this  separator  should  be  con- 
nected to  the  hot  well,  and  the  drip  should  be  returned  to  the  boiler 
with  the  loss  of  as  little  heat  as  possible. 

In  the  "Stratton"  separator,  Fig.  59,  the  steam 
enters  at  one  side  of  a  cylinder,  flows  down- 
ward, and  then  upward  through  a  pipe  in  the 
middle.  Dry  steam  escapes  from  a  pipe  near 
the  top,  on  the  opposite  side  from  which  it 
enters.  The  separated  water  is  drained  at  the 
bottom. 

The  "Cochrane"  steam  separator,  shown  in 
section  in  Fig.  GO,  is  of  the  baffle-plate  type. 
The  branches  for  the  entrance  and  exit  of 


Fig.  60.    Sectional  Elevation 
and  Plan  of  "  Cochraue  " 
Steam  Separator. 


Fig.  61.    Separator  Designed  for  Connection 
to  Main  Steam  Pipe  near  Engine. 


the  steam  project  from  each  side  of  the  spherical  head.  Another 
branch  from  the  bottom  provides  for  connection  with  the  well.  The 
baffle-plate,  which  is  cast  as  a  part  of  the  head,  is  ribbed,  or  corrugated, 
and  has  ports  at  each  side  for  the  passage  of  steam.  The  area  of  the 
ports  is  large,  to  prevent  loss  by  friction.  A  small  pipe  is  inserted 
in  the  plate  on  the  outlet  side  at  the  bottom  of  the  baffle-plate,  to  drain 


205 


64 


BOILER  ACCESSORIES 


any  condensation  in  the  outlet  chamber.  Steam,  entering  at  the  left- 
hand  opening,  strikes  the  baffle-plate  and  passes  to  the  outlet  chamber 
by  means  of  the  two  side  passages,  as  shown  in  the  plan,  Fig.  GO. 

A  form  of  separator  which  is  fitted  to  the  main  steam  pipe  near 
the  engine,  is  shown  in  Fig  .61.  Steam  enters  at  A  and  strikes  the 
dash-plate  B;  any  water  coming  with  the  steam  is  separated  and  falls 
to  the  bottom.  The  steam  takes  the  direction  indicated  by  the  arrows, 
and  flows  out  at  D.  This  separator  is  fitted  with  a  gauge-glass  which 
is  similar  to  a  boiler  gauge-glass. 

STEAM  TRAPS 

Steam  traps  are  used  for  collecting  the  water  of  condensation 
from  steam  pipes.  They  consist  of  a  receptacle  with  an  inlet  and 

outlet  valve  so  arranged 
that  the  condensation 
which  collects  may  flow 
out,  but  steam  cannot 
pass. 

In  the  float  trap  shown 
in  Fig.  62,  the  float  rises 
and  falls  with  the  change 


-  C2.    Simple  Steam  Trap  Operated  by  Float. 


in  Water-level.  When  the  water-level  rises  above  a  certain  point, 
the  float  opens  the  discharge  valve.  The  trap  shown  in  Fig.  63  is 
similar,  the  flbat  being 
replaced  by  a  weight 
IF,  which  is  nearly 
counterbalanced  b  y 
the  weight  T.  The 
raising  of  IF  by  the  wa- 
ter opens  the  valve  V. 
There  are  other 
forms  called  bucket 
traps.  In  the  one 
shown  in  Fig.  04,  the 
water  enter*  at  W.  While  there  is  only  a  little  water  around 
the  bucket  F,  >.  floats,  and  the  valve  V  is  closed;  but  when  the 
water  rises  hi.^i  enough  to  flow  over  the  edge,  the  weight  of  water  in  the 
bucket  canoes  it  to  sink,  nnd  opens  the  valve  V.  Water  is  forced  up 


I-  i0'.  03.    Steain  Trap  Operated  by  Neariy 
balanced  Weight. 


808 


BOILER  ACCESSORIES 


65 


N 


the  passage  M,  and  out  through  the  pipe  N,  by  the  pressure  of  the 
steam  on   the   sur- 
face   of   the    water 
surrounding     the 
bucket. 

Another  form 
of  trap,  called  the 
differential  steam 
trap,  depends  upon 
a  head  of  water 
acting  on  a  flexible 
diaphragm.  Water 
enters  at  either  top 
or  bottom  by  the 
pipes  E,  Fig  65. 
When  the  water- 
level  rises,  it  fills 


Fig.  61.    Bucket  Typo  of  Steam  Tiap. 


the  chamber  G  and  the  pipe  N.     This  causes  a  pressure  on  the  under 
side  of  the  diaphragm  greater  than  that  caused  by  the  spring  //, 

which  spring  acts  on  the  upper 
side  of  the  diaphragm  and  tends 
to  keep  the  valve  open.  While 
the  pressure  below  the  diaphragm 
preponderates,  the  valve  P  re- 
mains closed.  When  the  water 
rises  and  fills  the  chamber  J  so 
as  to  flow  down  the  pipe  M,  the 
water-pressure  on  the  upper  and 
lower  side  of  the  diaphragm  will 
become  equal,  because  the  head 
of  water  in  M  is  practically 
the  same  as  that  in  N.  The 
spring  will  now  open  the  valve  P, 
and  water  will  be  discharged 
from  the  pipe  7.  When  the 
head  in  M  falls,  the  pressure  on 

Fitc.  65.  Differential  Steam  Trap.  Operated  by  l 

Water-Pressure  on  a  Flexible  Diaphragm,      the  under  Side  ot  the  diaphragm 

again  becomes  greater,  and  the  valve  accordingly  closes. 


207 


66 


BOILER  ACCESSORIES 


Return  Traps.  Traps  that  are  used  for  returning  water  of  con- 
densation to  the  boiler  are  called  return  traps.  There  are  a  variety 
of  forms,  but  the  principle  of  action  in  all  is  similar,  and  is  shown  in 
Fig.  66.  B  represents  the  boiler,  and  T  the  trap,  which  is  placed  a 
few  feet  above  the  boiler.  The  trap  is  supplied  with  steam  from  the 
boiler.  It  is  also  connected  with  the  boiler  by  the  pipe  P,  in  which 
is  a  check-valve  at  C.  Water  of  condensation  enters  the  trap  through 
the  pipe  E,  in  which  is  a  check-valve  H,  until  it  reaches  a  depth 
sufficient  to  raise  the  float  F,  which  opens  the  balanced  steam  valve  V, 


Fig.  06.    Diagram  Illustrating  Operation  of  Return  Trap. 

called  an  equalizing  valve.  Steam  from  the  boiler  then  enters  the 
trap  and  equalizes  the  pressure.  Since  the  pressures  are  equal,  water 
in  the  trap,  because  of  its  height  above  the  water-level  of  the  boiler, 
will  flow  to  the  boiler  until  the  level  in  the  pipe  P  is  nearly  the  same  as 
the  water-level  in  the  boiler.  As  the  water-level  in  the  trap  falls,  the 
float  F  drops,  and  the  equalizing  valve  is  closed. 

In  some  forms  of  return  traps,  buckets  are  used  instead  of  floats. 

CALORI  METERS 

Steam  from  a  boiler  is  generally  accompanied  with  more  or  less 
moisture.  This,  being  mechanically  suspended  in  the  steam,  cannot 
readily  be  measured  without  the  use  of  special  apparatus.  An  instru- 


BOILER  ACCESSORIES 


67 


ment  by  means  of  which  the  percentage  of  moisture  in  steam  can  be 
determined,  is  generally  called  a  calorimeter.  There  are  several  dif- 
ferent types  of  this  instrument,  only  three  of  which  will  be  described. 
The  Barrel  Calorimeter.  This  was  invented  by  the  distinguished 
engineer,  Mr.  G.  A.  Him,  and  is  not  only  one  of  the  earliest  of  these 
devices,  but  is  by  all  means  the  simplest  and  most  inexpensive  form 
of  calorimeter  in  practical  use.  It  is  shown  in  Fig.  67.  The  essential 
apparatus  consists  of  a  barrel  holding  about  400  Ibs.  of  water,  scales 
for  weighing — and  nothing  more.  A  pipe  with  suitable  connections 
leading  from  the  boiler  or  steam  main,  conveys  the  sample  of  steam 
to  be  tested.  This  pipe  should  be  provided  with  a  valve,  and  on  the 
end  should  be  a  piece  of  rubber  hose  which  can  readily  be  inserted  in 
the  barrel  or  removed. 
The  principle  of  this  calor- 
imeter is  extremely  simple. 
As  steam  flows  through  the 
pipe,  it  is  condensed  by  the 
water  in  the  barrel,  and  the 
increase  in  the  weight  of 
the  barrel  after  the  test  in- 
dicates the  total  amount  of 
moist  steam  condensed, 
while  the  rise  in  tempera- 
ture of  the  Water  in  the  Fig.  G7.  Details  oi  Barrel  Calorimeter. 

barrel  is  an  exact  measure  of  the  quantity  of  heat  obtained  from  this 
moist  steam. 

The  steam  tables  give  the  number  of  B.  T.  U.  in  dry  steam  and 
hot  water  at  various  temperatures  and  pressures;  and  with  this  data 
and  the  above-mentioned  observations  made  in  the  barrel,  the  per- 
centage of  steam  and  moisture  can  readily  be  determined. 

The  sampling  pipe  usually  projects  into  the  steam  main  a  few 
inches,  the  end  being  perforated  so  that  the  sample  will  be  drawn  from 
a  point  near  the  middle  of  the  pipe.  An  agitator  should  be  placed 
in  the  barrel,  so  that  the  water  may  be  thoroughly  stirred  and  a  uni- 
form temperature  maintained  during  the  test. 

To  test  a  sample  of  steam  by  this  method,  fill  the  barrel  about 
two-thirds  full  of  cold  water;  place  it  on  platform  scales,  and  carefully 
note  its  weight  and  temperature.  The  weight  of  the  barrel  and 


200 


68  BOILER  ACCESSORIES 

fittings,  when  empty,  should  of  course  be  known,  so  that  the  weight 
of  the  water  alone  can  be  determined.  With  the  hose  removed  from 
the  barrel,  allow  steam  to  blow  through  the  pipe  until  it  has  become 
thoroughly  heated  If  the  sampling  pipe  is  long,  it  should  be  wrapped 
with  hair  felt  or  some  form  of  lagging,  to  prevent  condensation  during 
the  test.  As  soon  as  the  pipe  line  has  become  thoroughly  heated, 
plunge  the  hose  into  the  barrel  and  allow  the  steam  to  blow  through 
the  water  until  it  has  become  well  heated.  Shut  off  the  steam,  and 
carefully  note  the  weight  and  temperature. 

Suppose  W  =  Final  weight  of  water  in  barrel; 

w  =  Weight  of  cold,  condensing  water  before  steam  is  turned  on; 
d  =  Temperature  of  the  cold  water; 
lz  =  Temperature  of  the  hot  water; 

P  =  Absolute  pressure  of  steam  in  steam  pipe  (gauge  pressure  + 
atmospheric  pressure). 

From  the  steam  tables  in  the  back  of  the  book  may  be  found : 

q,   the  B.  T.  U.  in  one  pound  of  the  liquid  contents  of  the  moist  steam; 
t/i,  the  B.  T.  U.  in  one  pound  of  the  cooling  water,  before  the  steam  was 

added; 
</2,  the  B.  T    U.  in  one  pound  of  this  water  after  the  steam  has  been 

added ; 
r,   the  heat  of  vaporization  corresponding  to  the  absolute  pressure  —  i  c., 

B.  T.  U.  given  up  by  one  pound  of  steam  condensed  into  water. 

If  x  equals  the  percentage  of  dry  steam  contained  in  the  supply 
pipe,  1  —  x  will  represent  the  amount  of  priming. 

x  (W  —  w}  =  the  total  amount  of  dry  steam  condensed ; 

(1  —  x)  (W  —  w}  =  the  total  amount  of  moisture  brought  into 
the  barrel  by  the  moist  steam. 

If  ql  equals  the  heat  in  one  pound  of  cooling  water,  then  q^w  will 
equal  the  total  heat  in  the  barrel  at  the  beginning. 

For  the  same  reason  q2W  will  equal  the  total  heat  after  the  steam 
has  been  condensed,  and  q2  W  -  ql  w  will  equal  the  total  amount  of 
heat  gained  by  the  water  in  the  barrel. 

If  r  is  the  heat  of  vaporization,  then  r  x  (W -  w}  will  equal  the 
B.  T.  U.  contained  in  the  dry  steam;  and  if  q  is  the  heat  of  the  liquid 
corresponding  to  the  same  pressure,  then  q  (1  -  x)  (W  -  w)  will  equal 
the  B.  T.  U.  contained  in  the  moisture  brought  over  by  the  steam. 
It  is  apparent  that  the  sum  of  those  two  quantities  will  be  the  total 
number  of  B.  T.TJ.  brought  from  the  steam  main  to  the  water  barrel, 
and  must  be  equal  to  q2  W  -  ql  w,  the  heat  gained  by  the  water  in  the 


810 


BOILER  ACCESSORIES  69 

barrel.  The  solution  of  this  equation  will  result  in  a  formula  which 
will  save  some  mathematical  computations. 

That  the  method  may  be  perfectly  clear,  let  us  first  consider  a 
numerical  example  in  full. 

Suppose    w  =  "455  Ibs. 

W  =  495  Ibs. 

•h  =  50°  F. 

h  =  140°  F. 

P  =  75  Ibs. 

q  (from  steam  tables)  =  276  9 

9i       "         "  "        =  18.1 

</2       "          "  "         =  108.2 

Then  the  total  heat  in  the  barrel  after  condensation,  is  equal! 
to  (495  X  108.2)  -  53,559  B.  T.  U. 

The  total  heat  before  condensation  was  equal  to  455  X  18.1  = 
8,235  B.  T.  U.     Therefore  the  heat  brought  over  by  the  moist  steam 
will  be  53,559  -  8,235  =  45,324  B.  T.  U. 
Now,  from  the  steam  tables 

q  =  27G.9;  and  r  =  898.8. 

The  heat  given  Up  by  condensation   of   the  dry  steam  will   then  be 
898.8  X '(495- 455)z  =  4(X»  X  898.8  =  35,952^;  and  the  heat  of  the 
liquid  in    the  moisture  and  condensed  steam  will  be  40  X  270.9  = 
1 1 ,070,  making  the  total  heat  in  the  moist  steam  =  11,070  +  35,952.r. 
Therefore,  11,070  +  35,952.r  =  45,324 
35,952*  =  34,248 
x=  0.952 

That  is,  every  pound  of  moist  steam  contains  .952  lb.  dry  steam  and 
.048  lb.  moisture;  or  we  may  say  there  was  4.8  per  cent  of  priming. 
The  formula  may  be  derived  by  the  following  algebraic  work: 

Total  heat  in  bbl.  after  condensation  =  W  q2; 

Total  heat  in  bbl.  before  condensation  =  w  </, ; 

Total  heat  brought  over  by  steam  =  W  q.,  —  w  </t ; 

Heat  of  liquid  in  condensed  steam  =  (IF  —  w)  q; 

Latent  heat  in  dry  steam  =  x  (IF  —  U")  r; 

Total  heat  in  moist  steam  =  x  (IF  —  w)  r  +  (IF  -  w)  q. 

Therefore, 

X  (W-  W)  r  +  (IF  -  w)  q  =  W  q.z  -Wft: 
xr  (IF—  w)  =  IF  </2  —  w  ryt  —  IF  q  +  w  q; 

or,  transposing  to  a  more  convenient  form, 


£11 


BOILER  ACCESSORIES 


r  (W  - 

The  use  of  this  form  of  apparatus  is  not  especially  to  be  com- 
mended, for  it  is  liable  to  error,  and  a  slight  discrepancy  in  the  weights 
or  the  temperatures  may  cause  a  large  error  in  the  result.  In  the 
above  calculations,  no  allowance  is  made  for  loss  of  heat  through 
radiation. 

Separator  Calorimeter.  This  instrument  shown  in  Fig.  68, 
consists  of  a  chamber  A,  into  which  is  led 
a  steam  pipe  D,  bringing  a  sample  of 
steam  from  the  boiler  or  steam  main. 
This  pipe  leads  into  an  enlargement  per- 
forated with  small  holes,  or  into  a  cham- 
ber A  as  shown  in  Fig.  68.  The  calori- 
meter separates  the  moisture  from  the 
steam  just  as  a  steam  separator  does; 
and  the  exhaust,  which  is  dry  steam, 
passes  out  of  the  pipe  ,  wherein  is  in- 
serted a  diaphragm  containing  small  ori- 
fices, by  means  of  which  the  quantity  of 
steam  flowing  out  can  be  calculated  by 
thermodynamic  methods.  The  exhaust 
steam  can,  of  course,  be  led  to  some 
form  of  condensing  apparatus,  and  the 
condensation  weighed,  if  desired. 

As  the  steam  enters  the  calorimeter,  the 
moisture  is  drawn  toward  the  bottom  of 
the  chamber.  The  amount  of  water 
collected  can  readily  be  read  from  the 
gauge-glass  at  the  side,  to  which  a  gradu- 
ated scale  should  be  attached. 

The  amount  of  moisture  contained  in 
the  steam  can  be  weighed  directly  by 

drawing  it  out  of  the  gauge-cock  E.  The  amount  of  dry 
steam  is  measured  by  its  flow  through  the  orifices,  or  by  conden- 
sation.* If  W  =  weight  of  steam  discharged  from  the  calorimeter, 

*NOTE:  For  principles  governing  flow  of  steam  through  an  orifice,  consult  any 
treatise  on  Thermodynamics. 


Fig.  G8.     Separator  Calorimeter. 


BOILER  ACCESSORIES 


71 


and  w  =  weight  of  water  collected,  then  the  percentage  of  priming 


will  be 


W 


If  only  a  small  quantity  of  steam  is  used,  an  allowance  must  be 
made  for  condensation;  but  if  the  instrument  is  well  lagged  with 
hair  felt  or  other  suitable  material,  and  a  sufficient  quantity  of  steam 
is  used,  the  error  from  radiation  may  be  neglected.  Steam  should  be 

allowed    to    flow    pressureiriCdor,  Pressure 

through  the  instru-  ^~  MalnSteamPipev 

ment  until  it  has 
become  thoroughly 
heated,  before  be- 
ginning the  test. 

Throttling  Cal= 
o  r  i  m  e  t  e  r.  This 
was  invented  b  y 
Prof.  Cecil  H.  Pea- 
body,  and  is  made 
with  varying  con- 
structive details. 
Fig.  69  shows  the 
general  arrange- 
ment. The  mix- 
ture of  steam  and 
water  from  the 
boiler  is  taken  from 
the  main  steam 
pipe  through  what 
is  termed  a  sampling  pipe.  Various  forms  of,  this  pipe  are  made;  one 
arrangement  consists  of  a  pipe  closed  at  its  inner  end,  but  having 
numerous  holes  £  inch  in  diameter  drilled  staggering  around  the  sides. 
The  calorimeter  should  be  placed  as  close  as  possible  to  the  main 
steam  pipe;  and  the  gauge  for  indicating  the  pressure  in  the  main 
steam  pipe  should  be  placed  on  the  latter  and  near  the  calorimeter. 
The  gauge  is  sometimes  connected  to  a  tee  on  the  pipe  leading  to  the 
calorimeter;  but  it  is  better  to  have  this  gauge  where  the  velocity  of 
the  flowing  steam  is  less.  A  valve  is  placed  in  the  pipe  to  the  calori- 
meter, below  which  is  inserted  a  nipple  A  having  a  small  converging 


f  Gas  Pipe  - 
Globe  Valve 


Fig.  69.    General  Arrangement  of  Throttling  Calorimeter, 


213 


72  BOILER  ACCESSORIES 


orifice  D,  about  two-tenths  of  an  inch  in  diameter  and  very  carefully 
made.  The  object  of  such  an  orifice  is  to  determine  the  weight  of 
steam  flowing  through  the  calorimeter,  so  that  an  allowance  can  be 
made  for  the  loss  when  testing  an  engine  or  boiler,  where  the  net 
weight  used  is  required.  A  cup  B  is  screwed  into  the  top,  for  holding 
an  accurate  thermometer.  The  cup  is  made  of  brass,  and  is  filled  with 
oil;  but  if  mercury  is  used,  the  cup  must  be  of  iron  or  steel.  A  deli- 
cate gauge  C,  for  determining  the  pressure  in  the  calorimeter,  and  a 
pipe  and  valves  at  the  bottom,  complete  the  apparatus.  The  valve  N 
is  sometimes  omitted,  and  a  simple  pipe  used,  as  the  throttling  is  best 
accomplished  by  use  of  the  valve  E  or  orifice  D.  All  pipes  leading  to 
the  calorimeter  should  be  well  covered  with  a  good  non-conductor. 

To  use  the  instrument,  proceed  as  follows:  Open  wide  valves  E 
and  N,  to  bring  the  apparatus  to  a  uniform  temperature;  then  gradu- 
ally close  E  until  the  steam  in  the  calorimeter  is  superheated;  that  is, 
until  the  temperature  as  shown  by  the  thermometer  is  greater  than  that 
corresponding  to  the  absolute  pressure  determined  from  the  reading 
of  the  gauge  C  and  barometric  pressure.  The  result  may  now  be 
calculated  as  follows: 

x  =  Weight  of  steam,  contained  in  one  pound  of  the  mixture  from 
the  main  steam  pipe  or  other  source; 

\  =  Total  heat  corresponding  to  the  absolute  pressure  determined 
from  the  reading  of  the  gauge  C  and  barometric  pressure;  * 

T  =  Temperature  as  shown  by  the  thermometer; 

tc  —  Temperature  of  steam  corresponding  to  the  absolute  pressure 
as  determined  by  the  reading  of  the  gauge  C  and  barometric  pressure; 

</5  =  Heat  of  the  liquid  corresponding  to  the  absolute  pressure 
in  the  steam  pipe; 

rs  =  Heat  of  evaporation  corresponding  to  the  absolute  pressure 
in  the  steam  pipe; 

0.48  =  Heat  required  to  superheat  the  steam  one  degree  Fahren- 
heit under  constant  pressure. 

Total  heat  in  1  11  >.  superheated  steam  in  calorimeter  -  \  + 
(US  (T  -  Q  B.T.  U, 

Total  heat  in  1  11>.  moist  steam  in  steam  main  =  xrs  +  r/s  B.T.  U. 

These  two  quantities  are  equal;  and  x,  being  the  only  unknown 
quantity,  the  equation  can  easily  be  solved. 

*NOTE:  Some  steam  tables  use  //instead  of  the  Greek  letter  \  (lambda,). 


BOILER  ACCESSORIES 


7:; 


x  _ 


-  Q  -  gs 


Example.  Barometric  pressure,  14.78  Ibs.  Absolute  pressure 
in  main  steam  pipe,  87.78  Ibs.  Absolute  pressure  in  calorimeter, 
23.03  Ibs.  Temperature  (T)  =  260°  F.  Then, 

\=  1,153.68  9.  =  288.1 

4  =  235.28  n  =  890.88 

1,153.  B8  +  .48  (260  -  235.28)  -  288.1 

-J890T88~:  =0.984  pound. 

Or,  in  other  words,  98.4  per  cent  of  the  mixture  is  steam;  or  the 
moisture  =  1  —0.984  =  0.016,  or  1.6  per  cent. 

This  form  of  calorimeter  is  suitable  only  for  cases  where  the 
moisture  does  not  exceed  three  per  cent  of  the  mixture.  Its  principle 
is  based  upon  the  assumption  that  there  is  no  loss  of  heat,  in  which 
case  steam  mixed  with  a  small  amount  of  water  is.  superheated  when 
the  pressure  is  reduced  by  throttling. 

PIPING 

Although  piping  can  hardly  be  considered  a  boiler  accessory, 
a  few  general  remarks  will  not  be  out  of  place. 

Pipes  must  not  only  be  of  sufficient  size  and  strength,  but  should 
be   so  installed    as    to   make 
ample  provision  for  expansion 
due  to  the  high  temperature  f~~          /7r~  7\ 

when     they    are    filled    with  A  V 

steam.  The  supports  for  long 
pipe  lines  should  be  arranged 
somewhat  as  shown  in  Fig.  70, 
which  allows  the  pipe  a  con- 
siderable amount  of  lateral 


Fig.  70.    Side  and  Transverse  Sectional  Views 

Showing  Methods  of  Arranging  Supports 

for  Long  Pipe  Lines. 


motion. 

If  the  pipe  line  is  long, 
an  expansion  joint  must  be 
provided.  Sometimes  a  curved 
U-bend  may  be  inserted  in  the  pipe  line,  which  of  itself  will  have 
flexibility  enough  to  provide  for  reasonable  expansion.  Or,  if  the 
steam  main  is  not  all  in  one  line,  a  similar  bend  may  be  pro- 
vided, with  elbows  and  nipples,  as  shown  in  Fig.  71.  In  this 


215 


74 


BOILER  ACCESSORIES 


case,  any  expansion  of  the  -steam  main  will  cause  the  nipples  to  'turn 
slightly  in  the  elbows.  This  motion,  of  course,  is  slight,  but  it  is 
sufficient  to  prevent  rupture.  U-bcnds  and  swivel-joints  are  hardly 
practicable  in  large  pipe;  and  in  such  cases  a  slip-joint,  made  tight  by 
a  stuffing  gland,  is  usually  provided.  If  this  is  done,  great  care  must 
be  taken  that  the  steam  main  is  straight  and  in  perfect  alignment,  as 
the  pipe  may  otherwise  bind  in  the  expansion  joint  and  cause  much 
damage  from  leakage. 

In  marine  work,  especial  care  must  be  taken  that  the  pipe  lines 
are  not  so  rigidly  connected  together  that  they  will  be  injured  by  the 
working  of  the  ship.  This  can  readily  be  provided  for  by  laying 
the  pipe  in  such  a  way  as  to  provide  a  simple  form  of  swivel-joint. 

The  pipe  lines  should  be  as 
straight  as  possible,  to  prevent 
unnecessary  friction  of  the 
steam  and  unnecessary  con- 
densation; and  they  should,  if 
possible,  be  so  installed  as  to 
leave  no  pockets  wherein  con- 
densation may  collect.  If  such 
a  pocket  is  unavoidable,  a 


C 


SWIVEL-JOINT 


Fig  71.    Method  of  Forming  Swivel-Joint  i 
Steam  Piping  to  Counteract  Effects  of 
Expansion  and  Contraction. 


drain  must  be  provided,  lead- 
ing from  the  pocket  to  the 
steam  trap,  whence  the  con- 
densation may  be  discharged  into  tj|e  hot  well  or  filter-box,  because 
the  collection  of  water  in  steam  pipes  is  a  source  of  inconvenience 
and  danger. 

The  pipe  lines  should  be  installed  with  sufficient  slope,  so  that 
the  condensation  will  readily  drain  to  a  convenient  point  whence  it 
may  be  drawn  off.  This  slope  should  be  in  the  direction  of  the  flow 
of  the  steam,  as  the  water  will  not  readily  flow  otherwise.  Great 
care  should  be  taken  that  the  pipe  lines  nowhere  sag,  as  suck  a  de- 
pression will  collect  condensation.  This  may  cause  very  little  dis- 
turbance unless  the  pressure  of  the  steam  is  suddenly  raised,  in  which 
case  the  water  is  liable  to  flow  bodily  along  the  pipe;  and  if  it  does 
not  enter  the  cylinder  of  the  engin?  and  cause  damage  there,  it  will 
cause  a  serious  water-hammer  which  may  rupture  the  elbows  of  the 
pipe  and  may  endanger  life. 


216 


BOILER  ACCESSORIES  75 


Formerly,  when  low  pressures  were  used,  cast  iron  was  a  common 
material  for  a  main  steam  pipe  leading  from  the  boiler  to  the  engine, 
but  the  higher  pressures  of  to-day  require  the  best  wrought  iron  or 
steel.  In  marine  work,  copper  is  commonly  used;  but  with  the 
advent  of  higher  and  higher  pressures,  copper  fails  to  give  the 
requisite  strength,  and  it  has  to  be  reinforced  with  wire  or  iron 
bands.  At  pressures  not  over  150  Ibs.,  copper  pipes  may  be  used,  by 
the  British  Board  of  Trade  rules,  15  inches  in  diameter;  but  at  200 
Ibs.,  copper  pipes  are  not  allowed  over  10  inches  in  diameter.  For 
large  sizes,  riveted  iron  or  steel  pipe  may  be  used.  For  high  pres- 
sures, cast-steel  fittings  are  required  by  the  U.  S.  Steamboat  Inspec- 
tion rules.  There  was  always  danger  that  the  large  copper  pipe  would 
burst;  and  it  is  now  the  common  practice  to  use  steel  for  such 
purposes. 

Large  steam  pipe  is  made  in  sections  which  can  be  riveted  to- 
gether. The  small  sizes  are  fitted  with  the  ordinary  type  of  flange,  and 
the  sections  may  be  bolted  together,  a  suitable  gasket  being  used 
between  the  two  flanges  to  make  a  steam-tight  joint.  The  flanges  are 
machined  perfectly  smooth,  and  the  packing  may  consist  of  rubber  and 
fiber  reinforced  with  wire  insertion,  or  of  asbestos,  or  of  corrugated 
copper. 

The  true  inside  diameter  of  steam,  gas,  or  water  pipe  is  not  always 
the  same  as  the  size  of  the  pipe  as  popularly  known.  For  instance, 
what  is  called  "3-inch"  pipe  has  an  actual  inside  diameter  of  3.007 
inches,  and  3.5  inches  outside  diameter.  The  actual  sizes  of  pipe, 
inside  and  outside,  can  be  found  in  any  handbook  or  steamfitter's 
catalogue. 

LAGGING 

When  steam  pipes  are  exposed  to  the  air,  a  considerable  amount 
of  condensation  will  collect  in  them,  depending  on  the  condition  of 
the  surface  of  the  pipe,  on  the  difference  in  temperature  between  the 
steam  and  the  surrounding  air,  and  on  the  velocity  of  the  steam 
through  the  pipe.  This  condensation  will  cause  a  large  amount  of 
heat  to  be  lost  to  useful  work,  and  will  make  the  dangers  of  water- 
hammer  possible  unless  carefully  drained.  Tests  have  shown  thai 
about  2  B.  T.  U.  are  lost  per  square  foot  of  pipe  per  hour  per  dtgr«? 


217 


76  BOILER  ACCESSORIES 

of  difference  in  temperature.  While  the  loss  for  a  few  hours  is  not 
likely  to  be  great,  yet,  if  taken  for  an  entire  year  throughout  a  con- 
siderable length  of  pipe,  the  sum  total  will  be  very  large  indeed.  The 
following  table  gives  some  idea  of  the  loss  of  heat  through  bare  pipe  at 
200  Ibs.  pressure: 

HEAT  LOSSES  IN  BARE  PIPES 

B.  T.  U.  Loss 

PER  SQ.  FT. 
CONDITION  OF  PIPE  PER  MINUTE 

New  Pipe 11.96 

Painted  Glossy  Black 12.10 

Painted  Glossy   White 12  .02 

Fair  Condition 13 .84 

Rusty 14 .20 

Coated  with  Cylinder  Oil 13 .90 

Painted  Dull  Black 14  .40 

VARIATION  OF  HEAT  LOSS  WITH  PRESSURE 

HEAT  Loss 
B.  T.  U.  PER  SQ. 
PRESSURE  FT.  PER  MINUTE 

340 15.97 

200 13.84 

100 8.92 

80 8.04 

60 7.00 

40 5.74 

A  full  account  of  some  interesting  tests  can  be  found  in  a  paper 
entitled  Protection  of  Steam-Heating  Surfaces,  by  C.  L.  Norton,  Vol.  XIX, 
Proceedings  of  the  American  Society  of  Mechanical  Engineers,  1898,  from 
which  these  tables  have  been  taken. 

Pipe  Coverings.  To  make  this  loss  from  radiation  as  small  as 
possible,  it  is  customary  to  cover  the  pipe  or  boiler  with  some  material 
which  will  prevent  loss  of  heat  and  which  will  not  burn.  There  is 
considerable  difference  in  the  value  of  various  substances  as  preventa- 
tives  of  heat  radiation.  Their  value  varies  nearly  in  an  inverse  ratio 
to  their  conducting  power;  but  due  allowance  must  be  made  for  the 
possible  deterioration  of  the  pipe  covering.  The  following  table  gives 
the  relative  value  of  various  substances  with  reference  to  their  ability 
to  prevent  radiation  of  heat.  For  purposes  of  comparison,  the  value 
cf  wool  is  taken  as  the  standard : 


218 


"-'        <• 


INTERIOR  VIEW  OF  COCHRANE  HEATER  AND  PURIFIER  FOR  NON-CONDENSING  ENGINE 
Harrison  Safety  Boiler  Works,  Philadelphia,  Penna. 


BOILER  ACCESSORIES  77 

RELATIVE  VALUES  OF  VARIOUS  PREVENTATIVES  OF 
RADIATION  OF  HEAT 

Felt,  Hair,  or  Wool 100 

Asbestos  Sponge 98 

Air-Cell  Asbestos 89 

Mineral  Wool 08  —  83 

Carbonate  of  Magnesia G7  —  70 

Charcoal 03 

Sawdust 01  -  OS 

Asbestos  Paper 47 

Wood 40-55 

Asbestos,  Fibrous 30 

Plaster  of  Paris 34 

Air  Space  (Undivided) 22 

There  are  many  patented  coverings  which  are  very  efficient,  but 
they  are  too  numerous  even  to  mention.  The  above-mentioned  article 
from  the  Proceedings  of  the  American  Society  of  Mechanical  Engineers 
gives  the  results  of  tests  of  several  of  these  coverings.  A  good  pro- 
tection is  afforded  by  air  confined  in  minute  cells,  such  as  is  to  be  had 
in  the  air-cell  asbestos  board;  this  is  made  by  cementing  together 
several  layers  of  asbestos  paper  which  have  been  corrugated  or  in- 
dented by  machinery  so  as  to  form  minute  air-cells.  The  more 
minute  the  subdivision  of  these  cells,  the  better  the  protection  is  likely 
to  be.  Hair  felt  is  one  of  the  most  efficient  non-conductors,  because  it 
is  very  porous  and  contains  a  large  number  of  air-cells.  It  is  not  one 
of  the  best  coverings,  however,  because  it  is  liable  to  deteriorate,  and 
its  life  on  high-pressure  pipes  is  not  likely  to  be  more  than  four  or  five 
years.  On  low-pressure  work  it  may  last  for  a  considerably  longei 
time. 

Mineral  wool,  a  fibrous  material  made  from  blast-furnace  slag, 
is  an  efficient  and  noncombustible  covering,  but  is  brittle  and  liable 
to  fall  off. 

The  coverings  most  easily  applied  to  pipes  arc  those  applied  in 
sectional  form,  which  clasp  around  the  pipe  and  arc  fastened  by  brass 
bands  at  convenient  intervals.  Such  coverings  are  made  both  of 
asbestos  and  of  magnesia,  and  are  usually  of  about  1  inch  in 
thickness. 

A  good,  cheap  covering  can  be  made  by  wrapping  several  layers 
of  asbestos  paper  around  the  pipe,  and  then  covering  these  layers  with 
a  layer  of  hair  felt  perhaps  f  inch  thick,  the  whole  being  wrapped  in 


219 


78  BOILER  ACCESSORIES 


canvas.  On  low-pressure  steam  pipes  this  covering  will  last  ten  to 
fifteen  years. 

Cork  is  perhaps  one  of  the  most  satisfactory  coverings  from  the 
point  of  radiation  loss,  but  is  rather  more  expensive  than  asbestos  or 
magnesia. 

It  has  generally  been  tke  impression  that  it  is  not  economical 
to  cover  a  pipe  to  more  than  one  inch  in  thickness.  This  will  depend 
upon  the  cost  of  the  covering  and  the  length  of  time  it  is  likely  to  last. 
If  it  docs  not  last  more  than  five  years,  one  inch  is  probably  the  most 
economical  thickness;  but  if  the  life  of  the  covering  is  likely  to  be 
ten  years  or  more,  a  second  inch  in  thickness  can  be  applied  to  advan- 
tage. For  instance,  in  the  above-mentioned  tests,  in  the  case  of  "Non- 
pareil cork,"  increasing  the  thickness  from  one  to  two  inches  raised  the 
cost  from  $25  to  $30  per  100  square  feet,  and  increased  the  net  saving 
in  five  years  by  $10,  and  by  $30  in  ten  years.  A  third  inch  of  covering 
did  not  produce  saving  enough  to  pay  for  its  cost.  In  each  case  with 
the  asbestos  fire-board,  a  second  inch  in  thickness  showed  a  saving 
of  $20  in  ten  years,  while  the  third  inch  in  thickness  showed  an 
actual  loss  from  the  dollars-and-cents  point  of  view.  It  would  be 
well  to  remark  that  it  is  of  great  importance  that  the  pipe  covering 
should  be  kept  in  repair,  for  a  loose-fitting  covering  is  of  little  value. 

Boiler  Coverings.  Much  the  same  remarks  may  be  made  with 
regard  to  boiler  covering  as  have  been  made  with  regard  to  pipe 
covering,  except  that  the  covering  put  on  boilers  is  usually  somewhat 
less  efficient  and  is  applied  in  greater  thickness.  Probably  one  of  the 
best  coverings  for  a  marine  boiler — or,  in  fact,  for  any  internally- 
fired  boiler — is  a  layer  of  air-cell  asbestos  board,  covered  with  a  coating 
perhaps  two  inches  thick  of  magnesia  or  asbestos.  This  comes  in 
powder  form,  and  when  mixed  writh  water  can  be  readily  applied  with 
a  trowel.  Coverings  on  boilers  are  best  placed  directly  against  the 
shell  without  an  air-space,  so  that  any  leak  in  a  joint  or  rivet  will  reveal 
the  spot  by  moistening  the  covering;  otherwise  the  escaping  water  may 
run  down  through  the  air-space  and  appear  at  some  remote  point,  the 
leak  thus  being  difficult  to  locate. 

An  efficient  covering  for  boilers  is  made  of  either  magnesia  or 
asbestos  in  the  form  of  blocks  of  the  proper  curvature,  which  can  lie 
directly  against  the  boiler;  but  this  form  of  covering  is  rather  more 
expensive  than  the  asbestos  or  magnesia  cement.  To  secure  an  extra 


220 


BOILER  ACCESSORIES  79 

hard  finish  a  coating  of  plaster  of  Paris  may  be  put  on  outside  the 
magnesia  or  asbestos.  No  boiler  or  pipe  covering  should  contain 
sulphate  of  lime,  as  this  is  liable  to  cause  corrosion. 

If  an  internally-fired  boiler  is  properly  lagged,  there  is  little  danger 
that  any  large  amount  of  heat  will  be  lost,  as  the  heat  of  the  fire  must 
pass  through  the  water  before  radiating.  This  is  not  true  with  an 
externally-fired  boiler,  where  a  considerable  amount  of  heat  may 
radiate  through  the  brick  setting  of  the  boiler  without  coming  in 
contact  with  the  boiler  at  all.  The  setting  of  such  a  boiler  should 
be  arranged  with  properly  confined  air-spaces;  o  A  an  efficient  pro- 
tection from  the  radiation  of  heat  at  the  top  of  the  boiler  may  be  had 
by  allowing  a  slight  space  between  the  boiler  and  the  top  covering 
for  the  circulation  of  the  hot  gases  of  combustion.  These  arc  on  their 
way  to  the  chimney;  and  as  they  are  necessarily  hotter  than  the  water 
in  the  boiler,  they  prevent  radiation  at  this  point. 

HORSE=POWER  OF  BOILERS 

The  unit  which  we  call  the  horse-power  is  arbitrary.  Assuming 
that  30  pounds  of  steam  are  required  per  horse-power  per  hour  for 
an  average  engine,  this  unit  for  boilers  has  been  adopted. 

One  (1)  horse-power  is  the  evaporation  of  30  pounds  of  water 
per  hour,  from  a  temperature  of  100°  F.  into  steam  at  70  pounds  gauge 
pressure.  "This  is  considered  equivalent  to  the  evaporation  of  341 
pounds  per  hour  from  and  at  212°  F.  A  boiler  horse-power  is  equiv- 
alent to  33,327  B.  T.  U.  per  hour. 

As  all  boilers  do  not  generate  steam  at  the  same  pressure  and 
from  the  same  temperature  of  feed-water,  it  is  necessary  to  reduce  the 
actual  evaporation  to  an  equivalent  evaporation.  Unless  this  is  done, 
the  relative  performances  of  boilers  cannot  be  compared. 

For  this  comparison,  the  actual  evaporation  is  reduced  to  the 
equivalent  evaporation  from  and  at  212°  F.     That  is,  we  suppose 
the  water  to  be  fed  at  212°  and  evaporated  into  steam  at  212°. 
Let  W  =  Water  actually  evaporated  in  pounds; 

H  =  Total  heat  of  steam  above  32°  F.,  at  actual  absolute  pres- 
sure; 

T  =*  Temperature  of  feed  water; 

w  =  Equivalent  evaporation  from  and  at  212°  F. 

Since  966  B.  T.  U.  are  necessary  to  evaporate  one  pound  of  water 


221 


80 


BOILEK    ACCESSORIES 


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Di;«  ---  --a  ^^^-^-^  ^~±~~  «^,^^.-  §2221  §!B 


PUMPING    CONNECTIONS.    ST.    LOUIS    EXPOSITION. 

CARBONATE  OF    MAGNESIA    COVERINGS. 

The  Philip  Carey  Mfg.  Co. 


BOILER  ACCESSORIES  SI 

from  and  at  212°  F.,  the  equivalent  evaporation  maybe  found  from 
the  formula, 


TF  (LI  +  32  —  T]  =  96Gw,  or  w  - 

you 

Then  the  horse-power  of  the  boiler  is: 

II.  P.  -     —  • 

The  above  method  is  considerably  s'aortened  by  substituting  for 
the  quantity  -  — ('^r '  the  number  found  in  the  accompanying 

table  (page  SO)  which  corresponds  to  the  actual  feed-water  tempera- 
ture and  steam  pressure. 

For  example,  a  boiler  is  required  to  furnish  2,100  pounds  of 
steam  per  hour.  If  the  gauge  pressure  is  So  pounds,  and  the  feed- 
water  enters  at  50°  F.,  what  is  the  equivalent  evaporation,  and  what 
is  the  horse-power? 

From  the  table,  the  factor  for  So  pounds  pressure  and  50°  F.  is 
1  .204.  Then  the  equivalent  evaporation  would  be  1.201  X  2,100  = 

9  -,2S  4 
2,528.4  pounds;  and  ~  =  73  (approx.)  =  the  II.  P. 

CORROSION  AND  INCRUSTATION 

There  are  several  causes  which  tend  to  shorten  and  destroy  the 
life  of  every  boiler.  These  may  be  divided  into  two  general  classes, 
chemical  and  mechanical,  and  are  usually  the  result  of  improper  feed- 
water  or  of  improper  care.  Pure  water,  free  from  air  and  carbon 
dioxide,  has  no  evil  effect  on  the  iron;  but  all  natural  waters,  whether 
from  rain,  lake,  river,  or  sea,  contain  air  and  a  little  carbon  dioxide  in 
solution,  and  such  water  will  cau.se  iron  to  corrode,  even  though  no 
other  impurities  are  present. 

Sea  water,  heated  under  a  steam  pressure  of  30  Ibs.,  even  if  it 
contains  no  air,  will  liberate  a  small  amount  of  hydrochloric  acid, 
which  instantly  attacks  the  iron  of  the  boiler  unless  counteracted  by 
some  chemical  agent. 

Hxternal  Corrosion.  There  are  two  forms  of  corrosion,  external 
and  internal.  External  may  be  due  to  faulty  setting,  to  improper  care, 
or  to  moisture  from  external  sources  or  from  leakage  from  joints  and 


223 


82  BOILER  ACCESSORIES 

valves.  A  large  amount  of  external  corrosion  is  the  result  of  setting 
boilers  in  a  mass  of  brickwork,  which  readily  absorbs  moisture,  and 
which,  when  not  under  fire,  is  likely  to  keep  the  boiler-plates  damp. 
The  exterior  of  a  boiler  encased  in  brickwork,  moreover,  is  not  so 
easily  accessible,  and  a  considerable  amount  of  deterioration  may  take 
place  without  being  readily  detected.  The  leakage  from  a  joint,  al- 
though slight,  may,  if  long  continued,  badly  corrode  the  boiler. 

Internally-fired  boilers  are  supported  on  saddles  and  are  easily 
accessible;  and  the  magnesia  or  asbestos  lagging  with  which  they  are 
usually  covered  will  tend  to  absorb  a  certain  amount  of  moisture.which 
will  be  given  off  when  hot,  thus  helping  to  keep  the  boiler  dry.  If  a 
leak  occurs  of  appreciable  size,  the  covering  will  become  softened  and 
its  presence  will  be  detected  at  once,  and  repairs  can  be  made  before 
any  serious  damage  is  done.  The  exterior  of  an  internally-fired 
boiler,  being  at  all  times  accessible,  can  be  properly  taken  care  of, 
which  is  not  true  of  a  boiler  set  in  brickwork.  Rivets  and  riveted 
joints  should  as  far  as  possible  be  kept  out  of  contact  with  the  fire. 

Internal  Corrosion.  This  is  the  result  of  the  chemical  action  of 
impure  feed-water.  It  may  occur  in  the  form  of  a  general  corrosion 
or  wasting-away  of  the  boiler-plates,  or  in  the  form  of  pitting  or 
grooving,  the  effects  of  which  are  likely  to  be  local.  Pitting  and 
general  corrosion  are  entirely  the  result  of  chemical  action,  while 
grooving  is  the  result  of  chemical  and  mechanical  action  combined. 

It  is  not  easy  to  discover  general  corrosion,  because  it  acts  more 
or  less  uniformly  over  a  large  surface.  Sometimes  the  rivet-heads 
rust  in  proportion  to  the  plates,  so  that  the  wasting-away  of  the  plates 
is  not  easily  noticeable.  A  uniform  corrosion  is  the  hardest  to  detect, 
and  can  usually  be  discovered  only  by  drilling  the  boiler  and  gauging 
the  thickness  of  the  plate.  If  the  thickness  of  the  plate  is  found  to  be 
materially  reduced,  the  working  pressure  of  the  boiler  should  be 
lowered  in  proportion. 

Sometimes  the  water  will  attack  the  plates  only  in  the  vicinity 
of  the  water-line,  in  some  instances  confining  the  damage  to  a  belt  (> 
inches  or  8  inches  wide.  Sometimes  a  few  rivets  below  water-level 
will  be  corroded,  the  rest  remaining  in  a  comparatively  good  con- 
dition. Often  the  stays  are  weakened  more  rapidly  than  the  plates, 
and  the  screw-threads  of  a  stay  may  be  badly  corroded  while  the 
shank  of  the  stay  remains  uninjured. 


224 


BOILER  ACCESSORIES  S3 

Pitting.  Fatty  acids,  which  are  likely  to  come  over  in  the  feed- 
water  if  vegetable  oils  are  used  to  lubricate  the  cylinder,  are  especially 
active  in  the  production  of  small  pits  throughout  the  interior  of  the 
boiler.  Pitting  appears  in  the  form  of  small  holes  or  in  patches  from 
j-  inch  to  1  inch  in  diameter,  or  even  as  irregularly  shaped  depressions. 
If  the  holes  are  small  and  close  together,  the  plate  is  said  to  be  honey- 
combed. It  is  generally  believed  that  this  phenomenon,  the  result  of 
chemical  action,  is  due  to  a  lack  of  homogeneity  in  the  material  of 
the  boiler,  although  an  entirely  satisfactory  explanation  has  not  yet 
been  given.  Pitting  may  also  be  caused  by  galvanic  action,  which 
may  take  place  especially  if  sea  water  is  used.  As  pitting  occurs 
when  there  is  no  cause  whatever  for  galvanic  action,  this  can  be  only 
a  secondary  cause  at  best.  It  is  reasonable  to  suppose  that  acids  will 
attack  the  most  susceptible  portions  of  the  plate;  and  if  there  is  any 
lack  of  homogeneity  in  the  iron,  it  is  probable  that  the  places  or  spots 
most  favorable  to  chemical  attack  will  suffer  first. 

Grooving.  Grooving  is  probably  the  result  of  straining,  springing, 
or  buckling  of  the  plates,  aided  by  local  corrosion  or  by  the  same  forces 
which  cause  pitting.  Straining  of  the  plates  may  be  due  to  insufficient 
or  improper  staying,  thus  causing  the  plates  to  spring  back  and  forth 
as  the  steam  pressure  varies.  This  phenomenon  is  most  commonly 
found  in  stationary  boilers  of  the  "Cornish"  or  "Lancashire"  types 
appearing  in  the  flat  end-plates  around  the  edge  of  the  angle  iron,  or 
in  the  root  of  the  angle  iron.  Too  rigid  staying  of  the  ends  by  gussets 
or  diagonal  stays,  or  too  great  a  difference  in  expansion  between  dif- 
ferent parts,  is  almost  sure  to  produce  grooves. 

Internal  grooving  may  be  caused  as  the  direct  result  of  excessive 
calking,  which,  by  injuring  the  surface  of  the  metal,  exposes  it  to  the 
corrosive  action  of  the  feed-water.  It  is  to  be  expected  that  if  strains 
which  cause  the  plates  to  come  and  go  are  set  up  in  the  boiler — 
especially  if  the  stresses  can  be  concentrated  along  a  definite  line — a 
weakness  will  be  developed  there,  and  it  will  be  a  susceptible  point 
for  chemical  attack.  Sometimes  grooving  is  so  fine  as  to  appear  to 
be  a  mere  crack.  But  the  crack,  although  perhaps  only  ^  inch  in 
width,  may  extend  into  the  plate  for  a  considerable  depth.  Grooves 
are  not  readily  detected,  and  if  allowed  to  continue  for  any  length  of 
time  are  likely  to  produce  serious  results. 


225 


84  BOILER  ACCESSORIES 

Prevention.  The  best  way  to  prevent  internal  corrosion  is  to 
use  water  that  has  no  corrosive  effect  on  the  plates.  If  internal  cor- 
rosion has  begun,  a  change  of  feed -water  may  prolong  the  life  of  the 
boiler,  but  in  many  instances  it  is  cheaper  to  build  a  new  boiler  than 
frequently  to  change  the  water  supply.  Sometimes  the  introduction 
of  a  thicker  plate  at  places  where  the  water  is  found  to  be  most  active 
will  be  advisable;  but,  as  these  plates  are  stronger  than  the  rest  of 
the  boiler,  the  strains  will  not  be  uniformly  distributed,  and  stresses 
are  likely  to  concentrate  along  the  edge  of  this  heavy  plate,  which  will 
be  a  susceptible  point  for  the  formation  of  grooves. 

The  acidity  of  the  feed-water  may  be  neutralized  by  some  alka- 
line substance,  such  as  soda,  before  it  enters  the  boiler.  The  amount 
of  soda  to  be  used  varies  with  the  acidity  of  the  water;  but  it  should 
always  be  used  in  the  smallest  possible  quantity,  as  the  soda  is  likely 
to  produce  priming  in  the  boiler  and  will  be  injurious  if  there  is  much 
salt  present.  Vegetable  oils  should  not  be  used  for  cylinder  lubri- 
cation if  the  condensation  is  to  be  fed  back  to  the  boiler,  as  such  oils 
contain  acids  which  will  always  produce  injurious  effects.  Mineral 
oils  alone  should  be  used. 

To  allow  for  a  general  corrosion,  ,10  inch  to  ^  inch  extra  thick- 
ness of  shell  should  be  provided.  All  seams  of  a  boiler  should  be 
tight,  and  no  welded  'tubes  should  be  used,  as  pitting  and  grooving 
are  likely  to  occur  in  the  vicinity  of  the  weld.  When  not  in  use,  no 
moist  air  should  be  allowed  in  the  boiler.  A  boiler  can  be  thoroughly 
dried  out  either  by  the  application  of  heat  or  by  placing  in  it  lime, 
which  will  readily  absorb  the  moisture. 

The  water  fed  to  the  boiler  should  be  thoroughly  filtered  to  re- 
move as  much  grease  as  possible,  for,  although  mineral  oil  is  not  likely 
to  cause  pitting, -it  has  a  serious  effect  in  the  formation  of  boiler  scale. 
Incrustation.  The  incrustation  formed  by  the  accumulation  of 
the  deposit  of  sediment  in  the  feed  water,  is  called  scale  or  sludge. 
The  solid  matter  in  the  feed-water  may  be  precipitated  by  the  rise 
in  temperature,  or  left  behin'd  as  the  result  of  the  evaporation  of  the 
water.  These  solids,  unless  blown  out,  are  liable  to  become  hardened 
on  the  inner  surface  of  the  boiler.  A  thin  coating  of  scale  in  itself 
is  beneficial,  for  it  keeps  the  water  from  direct  contact  with  the  iron, 
and  prevents  corrosion  and  pitting;  but  the  danger  is  that  if  a  thin 
scale  forms,  a  thicker  one  will  form,  and  this  heavy  scale,  being  a  poor 


BOILER  ACCESSORIES  85 


conductor  of  heat,  not  only  causes  considerable  waste  of  fuel,  but 
allows  the  plates  next  the  furnace  to  become  overheated,  with  the 
result  that  they  are  likely  to  give  way,  and  the  boiler  may  collapse. 

The  amount  of  solid  matter  in  solution  is  measured  in  grains  per 
U.  S.  gallon.  The  quantity  varies  greatly  in  waters  from  different 
sources,  but  is  seldom  over  40  grains  per  gallon.  It  is  not  the  quantity 
of  matter  in  solution,  but  its  nature,  that  determines  the  influence  of 
feed-water.  With  proper  attention  to  the  boiler,  the  presence  of  a 
certain  amount  of  carbonate  or  sulphate  of  soda  would  not  be  injurious ; 
while  the  same  number  of  grains  per  gallon  of  salts  of  lime  would 
cause  serious  trouble.  Salts  of  lime  (calcium),  together  with  car- 
bonate of  magnesia,  are  the  solids  most  frequently  found,  and  are' the 
most  troublesome.  Hard  water  contains  considerable  quantities  of 
lime.  So-called  soft  water  has  usually  but  little  solid  matter  in  sus- 
pension, but  it  may  contain  vegetable  or  organic  impurities  that  will' 
cause  corrosion  or  pitting. 

The  oil  used  in  the  engine  is  likely  to  get  into  the  boiler  through 
the  feed-water,  if  it  is  not  carefully  filtered  or  passed  through  a  yrcasc- 
exiractor.  The  oil  is  likely  to  be  deposited  on  the  sides  and  tubes  of 
the  boiler,  and  not  only  is  a  poor  conductor  of  heat,  but,  mingling 
with  the  sediment  which  is  precipitated  from  the  hot  water,  pro- 
duces a  mixture  which  is  readily  baked  onto  the  boiler-plates  and  is 
especially  obstinate  and  difficult  to  remove.  There  are  efficient 
grease-extractors  now  on  the  market,  which  will  remove  practically 
every  trace  of  oil. 

Carbonate  of  Lime.  Carbonate  of  lime  is  held  in  solution  in  water 
by  an  excess  of  carbon  dioxide.  As  the  water  is  heated,  the  excess  of 
carbon  dioxide,  or  carbonic  acid,  is  driven  off,  and  the  carbonates  will 
be  precipitated  in  the  form  of  a  whitish  or  grayish  sediment  of  the 
consistency  of  mud.  If  these  precipitates  are  not  mixed  with  im- 
purities, they  may  be  washed  out  of  the  boiler  after  it  has  been  allo  wed 
to  cool;  but  if  there  is  oil,  organic  matter,  or  sulphate  of  lime,  the 
deposits  are  likely  to  become  hard.  They  may  readily  be  drawn  off 
through  the  bottom  blow-out;  but  if  there  is  much  pressure  in  the 
boiler,  the  blow-out  valve  should  be  opened  only  for  a  very  short  time. 
If  a  considerable  amount  of  water  is  blown  out  while  the  boiler  is  still 
very  hot,  a  large  part  of  this  precipitation  is  likely  to  be  baked  onto  the 
tubes  and  interior  of  the  boiler  in  a  manner  thai  defies  removal.  Short 


227 


86  BOILER  ACCESSORIES 


and  frequent  blowings  will  accomplish  the  desired  result;  for  while 
the  boiler  is  in  uction  these  precipitates  are  more  or  less  in  motion,  and 
frequent  blowing  will  keep  the  boiler  clear.  Oil  and  various  organic 
matters  rising  to  the  surface  can  easily  be  removed  by  frequently 
opening  the  surface  blow-out. 

Sulphate  of  Lime.  This  troublesome  salt,  like  the  carbonate  of 
lime,  is  precipitated  with  a.  rise  of  temperature;  and  at  280°  F.,  none 
is  left  in  solution.  This  sediment  is  likely  to  form  a  hard,  adhering 
scale;  but  if  a  little  carbonate  of  soda,  or  soda  ash,  is  introduced  with 
the  feed  water,  calcium  carbonate  is  precipitated  in  the  form  of  a 
white  powder  which  can  be  readily  washed  out.  The  carbonate  of 
soda  should  be  introduced  at  regular  intervals,  a  portion  of  it  being 
dissolved  in  water  which  can  be  mixed  with  the  feed  in  the  hot  well. 
As  little  soda  as  possible  should  be  used,  as  it  is  likely  to  cause  priming 
'and  foaming.  The  hardness  of  the  scale  formed  by  the  sulphate  of 
lime  depends  on  the  other  impurities  in  the  water  and  on  the  tempera- 
ture; and  consequently  the  amount  of  soda  that  can  safely  be  used  can 
be  determined  only  by  trial.  Ammonium  chloride,  commonly  called 
sal-ammoniac,  is  sometimes  used  to  break  up  these  lime  compounds, 
but  is  not  always  desirable,  as  it  may  break  up  the  chlorides  if  other 
conditions  are  right,  thus  forming  free  chlorine,  which  attacks  the 
boiler. 

Carbonate  of  Magnesia  is  seldom  found  in  such  large  quantities 
as  calcium  salts.  Like  the  carbonate  of  lime,  it  is  precipitated  in  hot 
water.  If  there  is  any  oil  or  organic  matter  present,  it  is  likely  to 
form  an  injurious  precipitation. 

Iron  Salts  form  a  reddish  incrustation  which  is  very  injurious  to 
boiler-plates.  Brakish  water  containing  chloride  of  magnesium  is 
also  injurious;  for,  when  heated,  the  chloride  decomposes,  forming 
magnos-u  and  hydrochloric  acid,  the  latter  rapidly  corroding  iron. 

A  piece  of  thick  scale  broken  from  the  plates  of  the  boiler,  will 
show  a  series  of  layers  of  various  thickness,  some  of  them  crystalline 
and  some  amorphous.  Between  these  hard  layers  are  frequently 
found  layers  of  soft  or  earthy  matter. 

Nothing  definite  is  known  in  regard  to  the  loss  of  heat  caused  by 
scale  on  heating  surfaces,  for  there  are  too  many  circumstances  to  be 
considered  to  admit  of  exact  calculation.  It  has  been  stated  that  a 
layer  jV,  inch  th::k  in  tl.o  tubes  of  multitubular  boilers,  is  equivalent 


228 


BOILER  ACCESSORIES  87 


to  a  loss  of  from  15  to  20  per  cent  of  fuel.  The  loss  increases  rapidly 
with  the  thickness  of  the  scale.  A  uniform  coating  of  scale  is  not 
nearly  so  harmful  as  irregular  deposits,  for  in  the  latter  case  the  evil 
effects  of  overheating  are  likely  to  be  produced,  and  overheating  will 
result  where  it  is  least  suspected. 

Prevention.  Incrustation  may  be  prevented  by  precipitating  the 
scale-forming  substances  before  the  feed -water  reaches  the  boiler, 
by  the  introduction  of  chemical  compounds  to  neutralize  the  evil 
effects,  or  by  removing  the  sediment  before  it  becomes  hard.  Scale 
may,  of  course,  be  removed  by  hand  from  the  interior  of  the  boiler;  but 
this  is  a  slow  and  tedious  process.  One  of  the  chief  objections  to 
removing  scale  by  hand  is  that  the  surfaces  of  the  boiler  are  likely  to 
become  abraded  by  the  chipping  tools,  and  this  offers  excellent  oppor- 
tunity for  pitting  and  local  corrosion  to  set  in. 

Scale  has  sometimes  been  removed  by  blowing  the  boiler  off  at 
comparatively  high  pressure,  and  then  filling  it  with  cold  water.  This 
causes  a  severe  contraction  of  the  plates,  and  is  likely  to  loosen  the 
scale;  but  it  will  at  the  same  time  cause  serious  injury  to  the  boiler, 
and  is  a  practice  that  should  not  be  tolerated. 

After  the  impurities  are  deposited  in  the  boiler,  they  may  l>e 
removed  by  the  blow-out  apparatus;  and  if  it  is  possible  to  "lay  off" 
the  boiler  occasionally,  it  should  be  allowed  to  cool  down  slowly,  and 
then  the  water  may  be  drawn  off  and  the  boiler  properly  washed  out. 
A  considerable  amount  of  heat  is  abstracted  from  the  boiler  by  fre- 
quent blowing-off,  and  this  is  a  matter  of  direct  loss,  but  it  is  nothing 
like  so  much  as  would  be  caused  by  the  formation  of  scale. 

Water  may  be  purified  to  a  certain  extent  by  passing  it  through 
a  purifier  before  allowing  it  to  enter  the  boiler.  The  carbonate  and 
sulphate  of  lime  are  precipitated  at  the  same  time  that  the  water  is 
heated.  The  purifier  was  referred  to  under  the  topic  of  "Feed- 
Water  Heaters."  The  use  of  soda  for  the  neutralization  of  sulphate 
of  lime  has  already  been  spoken  of;  but  various  compounds  are  on 
the  market  for  overcoming  the  evil  effects  of  other  solids;  and  it  is 
possible,  by  an  analysis  of  the  feed  water,  to  prescribe  a  boiler  com- 
pound that  will  give  satisfactory  results.  Cheap  compounds,  sold 
without  reference  to  the  analysis  of  the  feed-water,  should  be  avoided. 
Caustic  soda  may  be  used  instead  of  the  carbonate,  but  should  be  used 
in  small  quantities.  A  rapid  circulation  of  the  water  will  prevent  the 


88  BOILER  ACCESSORIES 


formation  of  scale,  the  sediment  being  swept  from  the  tubes  or  shell 
into  the  mud-drum,  whence  it  may  be  blown  off.  This  is. one  of  the 
chief  advantages  claimed  for  water-tube  boilers. 

Zinc  plates  have  frequently  been  used  to  prevent  corrosion  and 
incrustation.  The  brass  fittings  are  likely  to  set  up  a  galvanic  action 
with  the  steel  plates;  but  if  the  zinc  is  put  in,  it  will  be  acted  upon 
instead  of  the  iron,  which  otherwise  might  be  rapidly  wasted.  It  is 
claimed  that  this  galvanic  action  prevents  the  formation  of  scale  by 
liberating  hydrogen  at  the  exposed  surfaces.  The  zinc  neutralizes 
the  free  acids  by  combining  with  them,  and  takes  the  place  of  iron 
in  causing  precipitation  of  copper  salts  when  present. 

Kerosene  oil  is  used  to  a  considerable  extent  to  prevent  the  forma- 
tion of  scale  and  to  assist  in  its  removal.  It  breaks  up  and  loosens 
hard  scale,  and  prevents  its  formation.  About  one  (mart  a  day  is 
siiflu-ient  for  each  100  horse-power  of  the  boiler. 

BOILER  EXPLOSIONS 

tiafcly  is  one  of  the  first  requisites  in  a  steam  boiler,  and  must  be 
assured  not  only  by  proper  design  in  the  beginning,  but.  by  subsequent 
care  and  proper  maintenance.  The  evil  effects  of  corrosion  and 
incrustation  have  been  clearly  shown;  and  it  is  apparent  that  a  boiler 
\\liirh  has  suilered  materially  from  either  cause  is  not  in  condition  to 
stand  full  steam  pressure.  Since  the  explosion  of  a  boiler,  especially 
in  a  city  or  a  factory,  is  likely  to  prove  fatal  to  many  people  and  to 
cause  the  destruction  of  considerable  property,  not  only  by  the  ex- 
plosion itself  but  also  by  fire,  which  almost  invariably  follows  such  an 
occurrence,  it  is  impossible  to  lay  too  great  emphasis  on  the  necessity 
of  seeing  that  the  boiler  is  in  proper  working  condition. 

All  boilers  must  be  carefully  tested — land  boilers,  by  the  State 
Inspectors;  marine  boilers,  by  the  United  States  Inspectors.  The 
boilers  are  carefully  examined  inside  and  outside,  and  subjected  to  a 
hydraulic  pressure  test  50  per  cent  greater  than  the  designed  pressure 
of  steam;  and  if  there  is  the  slightest  sign  of  pitting  or  corrosion,  the 
boiler-plates  may  be  drilled  and  the  thickness  calipered,  the  hole  being 
refilled  by  a  proper  plug.  If  a  boiler  passes  inspection,  a  subsequent 
explosion  will  probably  be  the  result  of  mismanagement,  although 
inspection  is  not  infallible. 


230 


I! 


BOILER  ACCESSORIES 


The  owner  of  the  boiler  is  usually  held  liable  in  case  of  explosion; 
but  may  protect  himself  from  financial  loss  by  insurance  against 
accident  in  any  of  the  boiler  insurance  companies.  If  so  insured,  the 
Insurance  Inspector,  as  well  as  the  State  Inspector,  examines  the 
boiler;  and  there  is  consequently  less  likelihood  of  an  explosion,  for 
an  insurance  inspector  will  naturally  be  exceedingly  careful  in  th? 
interests  of  his  company. 

The  damage  done  by  an  explosion  is  due  to  the  energy  stored  in 
the  hot  water,  which  energy  can  be  calculated  by  thermodynamic 
methods.  If  a  boiler  contains  a  large  quantity  of  water  at  high  pres- 
sure, and  that  pressure  is  suddenly  relieved,  as  would  happen  in  ease 
of  rupture,  a  considerable  portion  of  this  large  volume  of  water  will 
be  turned  instantly  into  steam,  and  the  resulting  explosion  will  ensue. 
\Vhen  a  fracture  starts  in  a  boiler-plate,  the  steam  escaping 
through  the  rent  or  opening  tends  to  diminish  the  pressure  rapidly 
within  the  boiler;  and  this  causes  the  rapid  formation  of  a  large 
amount  of  steam.  It  must  be  remembered  that  the  water  in  the  boiler 
at  high  pressure  is  held  in  the  form  of  water  only  because  of  the  high 
pressure  exerted  on  it.  If  this  pressure  is  relieved,  large  quantities  of 
water  will  evaporate  into  steam  at  once,  without  the  application  of 
further  heat.  This  almost  instantaneous  formation  of  a  large  quantity 
of  steam  prevents  the  boiler  pressure  from  dropping,  and  the  fracture 
naturally  widens.  The  larger  the  body  of  hot  water,  the  greater  the 
disaster.  This  accounts  for  the  relative  safety  of  water-tube  boilers. 
The  division  of  the  water  in  such  a  boiler  into  small  masses  in  different 
sections,  prevents  a  violent  explosion.  Should  a  water  tube  burn 
out,  probably  nothing  more  serious  would  happen  than  the  rapid 
escape  of  a  considerable  quantity  of  steam,  which  might  fill  the  boiler- 
room,  drive  out  the  attendants,  and  ultimately  cause  the  destruction 
of  the  boiler  because  of  the  absence  of  water  together  with  a  hot  fire. 
It  would  be  necessary  for  several  water  tubes  to  burst  at  once  in  order 
that  there  should  be  serious  damage  from  such  an  accident. 

Energy.  The  available  energy  in  one  pound  of  hot  water  at 
150  Ibs.  absolute  pressure  and  35S°  R,  is  about  42,800  foot-pounds; 
that  is,  it  is  sufficient  to  move  one  pound  nearly  eight  miles;  and  if  at 
250  Ibs.  pressure,  it  has  sufficient  energy  to  move  it  nearly  twelve 
miles.  This  energy  may  be  determined  somewhat  as  follows:  From 
the  table  of  the  properties  of  saturated  steam,  given  in  the  back  of  the 


231 


90  BOILER  ACCESSORIES 


hook,  it  is  scon  that  at  150  Ibs.  absolute  pressure  (approximately  135 
gauge),  the  temperature  is  35S.2G0  F.  The  heat  contained  in  a  pound 
of  hot  water  at  this  temperature  will  be  330  B.  T.  U.,  equivalent  to 
330  X  778  =  256,740  foot-pounds.  This  represents  the  total  heat 
energy  in  one  pound  of  hot  water  at  boiler  pressure;  but  since  one 
pound  of  steam  at  atmospheric  pressure  contains  very  many  more 
heat  units  than  a  pound  of  water  at  150  Ibs.  pressure,  it  is  apparent 
that  only  a  portion  of  this  water  can  evaporate  into  steam,  the  balance 
remaining  as  hot  water.  About  17  per  cent  of  the  total  energy  will  be 
thus  available  in  vaporizing  the  water  into  steam;  or,  approximately, 
42,800  foot-pounds  per  pound  of  water  will  be  developed.  The 
remaining  heat  is  in  the  form  of  hot  water. 

A  cylindrical  boiler  5  feet  in  diameter  and  10  feet  long  is  likely  to 
contain  about  G,000  pounds  of  water  and  22  pounds  of  steam.  Neg- 
lecting the  energy  of  the  steam,  which  is  relatively  small,  the  energy 
in  the  water  due  to  its  expansion  from  water  at  boiler  pressure  into 
steam  at  atmospheric  pressure,  will  be  approximately  0,000  X  42,800 
-  282,480,000  foot-pounds,  or  141,240  foot-tons. 

A  marine  boiler  13  feet  in  diameter  and  12  feet  long  would  develop 
approximately  twice  this  energy,  which  would  be  about  equivalent 
to  the  energy  developed  by  the  explosion  of  a  ton  of  gunpowder.  The 
explosion  of  one  boiler  on  a  modern  battleship  would  develop  sufficient 
power  to  lift  the  ship  completely  out  of  the  water.  Of  course  it  must 
be  realized  that  a  large  part  of  this  energy  is  lost,  and  considerable  is 
consumed  in  the  destruction  of  the  boiler  itself,  which  leaves  but  a 
comparatively  small  amount  to  be  expended  in  wrecking  the  im- 
mediate surroundings;  but  it  nevertheless  is  a  fact  that  the  energy 
developed  in  the  explosion  of  a  large  boiler  is  almost  beyond  the  power 
of  comprehension. 

Causes  of  Explosions.  Boiler  explosions  are  usually  the 
result  of  low  water,  grease,  or  scale.  The  two  latter,  by  preventing 
the  transmission  of  heat  from  the  water,  are  likely  to  cause  undue 
overheating  of  the  furnaces  or  tubes,  which  may  result  in  their  collapse ; 
these  two  causes — grease  and  scr.le — have  been  discussed  under  the 
subject  of  "Incrustation." 

Low  water  may  be  caused  by  failure  of  the  water  glass  to  indicate 
properly  the  amount  of  water  in  the  boiler,  or  by  failure  of  the  feed 
pump  to  work  properly. 


BOILER  ACCESSORIES  91 


Safety-valves  have  been  known  to  he  rusted  to  their  seats  so 
tightly  that  they  failed  to  work  at  the  proper  time. 

It  is  seldom  that  a  boiler  can  fail  as  the  result  of  defective  design, 
for  the  laws  in  regard  to  construction,  especially  of  marine  boilers,  are 
very  definite.  Defective  workmanship  or  material,  however,  cannot 
be  easily  discovered;  and  it  is  possible  that  corrosion  or  incrustation 
may  take  place  locally,  without  being  readily  detected;  and,  indeed, 
boiler-plates  may  even  be  tapped,  and  their  thickness  calipered, 
without  discovering  small  local  weaknesses  which  later  may  cause 
disaster.  Minute  fractures  which  escaped  the  Inspector's  detec- 
tion have  later  become  serious.  The  majority  of  explosions  can 
undoubtedly  be  traced  to  mismanagement  in  either  care  or  operation. 

Defective  Design.  If  a  boiler  is  improperly  set;  if  the  stays  are 
too  small,  too  few,  or  cut  or  bent  to  clear  floats,  pipes,  etc.,  danger  is 
likely  to  result  therefrom.  All  manholes,  large  handholes,  or  domes 
should  be  strengthened  with  a  reinforcing  plate  to  make  up  for  the 
material  cut  out.  If  the  boiler  is  set  too  rigidly  on  its  seating,  without 
proper  provision  for  its  expansion,  trouble  is  likely  to  follow.  A 
defective  water  circulation  is  likely  to  cause  excessive  incrustation  and 
unequal  expansion  of  the  plating,  which  is  liable  to  open  seams  and 
produce  fractures  in  the  plates. 

Deterioration.  The  strength  of  a  boiler  is  likely  to  be  impaired 
by  fractures,  general  corrosion,  pitting,  or  grooving.  But  external 
corrosion  is  the  cause  of  many  disasters.  It  proceeds  unnoticed  in 
many  cases,  and  rupture  may  occur  when  least  expected.  In  the  dis- 
cussion of  "Corrosion,"  it  was  shown  that  improper  setting  of  the 
boiler  would  cause  or  at  least  aggravate  external  corrosion;  and  that, 
on  account  of  the  close  setting  of  the  boiler,  it  was  not  easy  to  get  at 
the  plates  to  examine  them.  The  strength  of  a  boiler  originally  suf- 
ficient to  sustain  high  pressure  may  become  suddenly  reduced  by  over- 
heating or  over-straining,  either  of  which  weakens  the  plates.  Over- 
heating may  be  caused  by  poor  circulation,  lack  of  water,  or  the  accu  m- 
ulation  of  sediment  or  scale.  Over-straining  is  caused  by  sudden 
cooling  and  contraction,  or  equally  by  sudden  expansion.  In  starting 
the  fire  in  a  Scotch  boiler — or,  in  fact,  in  any  boiler  with  a  large  quan- 
tity of  water — care  must  be  taken  that  the  fire  is  started  slowly,  or  the 
boiler,  becoming  overheated  locally,  will  develop  excessive  strains. 


92  BOILER  ACCESSORIES 

Dejects  of  Workmanship..  Defective  workmanship  is  not  of  so 
frequent  occurrence  under  present  conditions  as  formerly,  when  many 
defects  used  to  be  produced  by  careless  punching  of  plates;  but  for 
most  boilers,  and  for  all  marine  boilers  at  present,  punching  is  pro- 
hibited; the  holes  must  be  drilled,  and  the  plate  edges  planed  and 
carefully  calked.  A  rigid  inspection  of  material  is  required,  ami  there 
seems  little  danger  of  unsatisfactory  work.  Cheap  boilers  may  of 
course  be  subject  to  various  defects,  but  a  good  boiler  should  be  free 
from  such  troubles.  Material  may  be  defective  and  may  not  be 
readily  detected;  but  the  careful  tests  now  required,  especially  in 
marine  work,  reduce  these  possibilities  to  a  minimum. 

Mismanagement.  The  pressure  in  a  steam  boiler  may  rise 
above  that  at  which  the  safety-valve  has  been  set  to  operate,  because  of 
corrosion  or  overloading  of  the  valve.  Stop-valves  are  sometimes 
placed  between  the  boiler  and  the  safety-valve;  but  this  practice 
should  be  condemned,  as  it  is  possible  that  the  stop-valve  may  be 
closed  when  the  fireman  thinks  the  safety-valve  is  open  to  the  boiler 
pressure.  If  the  size  or  lift  of  the  safety-valve  is  too  small,  steam  may 
be  generated  faster  than  it  can  escape,  in  which  ease  the  pressure  "will 
rise  in  spite  of  the  safety-valve.  It  has  been  claimed  that  the  blowing- 
off  of  the  safety-valve  when  the  boiler  is  und-er  excessive  pressure  may 
be  the  cause  of  starting  an  explosion ;  but  the  reason  why  this  should 
be  so  does  not  seem  to  be  especially  clear,  and  it  seems  to  be  improb- 
able if  the  opening  of  the  safety-valve  is  sufficient  to  cause  a  reduction 
in  pressure.  Safety-valves  have  sometimes  been  loaded  down  tem- 
porarily to  prevent  leakage  at  working  pressure;  but  such  a  practice 
is  little  short  of  criminal.  If  a  safety-valve  leaks,  it  should  be  re- 
ground,  but  under  no  circumstances  should  the  weight  on  the  lever  be 
altered. 

It  is  a  common  idea  that  when  the  furnace  plates  become  very 
hot,  perhaps  heated  to  redness,  due  to  a  lack  of  water,  and  the  feed  is 
turned  on,  a  violent  explosion  is  sure  to  follow.  Experiments  show 
that  when  a  piece  of  wrought  iron  is  heated  to  redness  and  plunged 
into  a  weight  of  water  three  or  four  times  greater  than  that  of  the  iron, 
a  comparatively  small  quantity  of  steam  is  disengaged.  There  is  no 
reason  to  believe  that  this  quantity  would  be  greater  if  the  iron  were 
jn  the  form  of  a  boiler  than  in  the  form  of  a  plate.  If  a  small  quantity 
of  water  were  admitted  to  hot  plates,  the  danger  would 


234 


BOILER  ACCESSORIES 


be  greater;  and  while  a  boiler  under  this  condition  might  explode, 
the  comparatively  small  quantity  of  water  in  it  would  make  the"  re- 
sulting danger  much  less  than  if  the  boiler  were  under  working  con- 
ditions. 

The  following  experiments  illustrate  the  action  of  cold  water  on 
hot  plates.  A  boiler  25  feet  long  and  G  feet  in  diameter  was  heated 
red  hot  and  the  feed  turned  on.  No  explosion  occurred ;  but  the  sud- 
den contraction  of  the  overheated  plates  caused  the  water  to  pour  out 
in  streams  at  every  seam  and  rivet-hole  as  far  as  the  fire-mark  extended. 
In  another  instance,  the  water  was  almost  entirely  drawn  off  while  the 
fires  were  burning  briskly.  When  the  remaining  water  had  been  con- 
verted into  steam  and  all  the  fusible  plugs  melted  out,  water  at  the  rate 
of  28  gallons  per  minute  in  a  series  of  fine  jets  was  played  on  the  hot 
plates.  Such  treatment  may  ruin  a  boiler  for  further  service,  though 
the  boiler  may  not  explode. 

That  a  tough  paper  or  cloth  is  easily  torn  when 'once  a  tear  is 
started,  is  a  well-known  fact.  Similarly  a  boiler-plate  may  be  rup- 
tured at  slight  pressure  if  a  fracture  has  been  started. 

The  position  of  the  fracture  or  hole  has  a  great  influence  on  the 
results.  In  case  a  large  rent  occurs  at  the  top  of  a  cylindrical  boiler, 
the  steam  and  hot  water  may  blow  out  of  the  hole;  and  the  boiler,  if 
strongly  enough  seated  to  stand  the  reaction,  will  remain  on  its  seat. 
The  damage  to  the  boiler  would  be  slight.  But  suppose  the  same  rent 
were  situated  on  the  under  side  of  the  boiler  near  the  ground  or  floor; 
the  effect  would  be  very  different,  the  reaction  of  the  escaping  steam 
would  probably  blow  the  whole  boiler  through  the  roof. 

Investigation.  When  an  explosion  occurs,  it  should  be  investi- 
gated, not  only  to  fix  the  responsibility  where  it  belongs,  but  also  to 
provide  for  and  take  means  to  prevent  future  disasters.  It  has  been 
customary  to  attribute  all  explosions  to  low  water,  since  it  is  an  easy 
way  to  throw  the  responsibility  from  the  makers  or  owners  upon  the 
fireman,  who,  even  if  living,  cannot  defend  himself.  In  the  investi- 
gation of  an  explosion,  the  weights,  shapes;  positions,  and  directions 
of  the  scattered  pieces  should  be  noted,  so  that  their  original  places 
may  be  known.  The  original  size  and  shape  of  the  boiler  and  of  the 
fittings  should  be  known  as  accurately  as  possible.  The  primary  rent 
may  be  discovered  from  comparison  and  from  deductions  of  the 
directions  taken  by  the  heavier  pieces.  Light  pieces  will  generally 


94  BOILER  ACCESSORIES 


take  the  direction  of  the  escaping  steam,  while  the  heavy  parts  take  ah 
opposite  direction,  that  of  the  reaction.  A  careful  examination  of  the 
pieces,  noting  the  age  of  fractures,  thickness  of  plates,  amount  of 
corrosion,  condition  of  plates,  etc.,  will  generally  show  the  cause.  A 
test  of  the  plates  will  in  many  cases  show  any  softening  or  yielding  to 
the  pressure  and  excessive  thinness  caused  by  bulging. 

Prevention.  The  means  taken  to  prevent  boiler  explosions 
from  most  of  the  above-mentioned  causes,  have  already  been  given. 
It  is  of  primary  importance  that  at  the  start  only  a  well-designed  and 
well-made  boiler  should  be  used.  The  matter  of  type  is  not  of  so 
much  importance;  but  it  is  well  to  use  a  sectional  boiler  in  large  cities 
or  in  buildings  where  many  people  are  employed.  There  are  many 
methods,  some  of  which  have  been  discussed,  that  are  taken  to  pre- 
vent deterioration  by  corrosion,  fracture,  etc.  Proper  setting  is  of 
great  importance  in  this  matter.  Mishaps  from  mismanagement 
may  be  greatly  lessened  by  the  employment  of"  licensed  attendants. 
A  boiler  should  never  be  in  the  hands  of  a  man  who  is  not  thoroughly 
competent  to  run  it.  The  most  effective  method  to  prevent  explosions 
is  the  law  of  the  State,  compelling  regular,  thorough  inspection  and 
licensed  firemen.  The  inspection  by  the  Boiler  Insurance  companies 
is  also  an  efficient  method. 

During  a  period  of  eleven  and  one-half  years,  70,000  boilers  were 
inspected  by  Boiler  Insurance  companies.  It  was  estimated  that  there 
were  140,000  in  use  during  that  time.  Of  the  inspected  boilers,  there 
were  23  explosions  and  50  collapses,  resulting  in  27  deaths  from  ex- 
plosions, and  28  deaths  from  collapses.  The  explosion  rate  was  1  in 
11,000;  and  the  death  rate,  1  in  14,000.  The  uninsured  boilers  did 
not  make  so  good  a  showing,  the  death  rate  being  1  in  5,000  boilers, 
or  about  3  times  as  high  as  among  the  insured  boilers, 

FUEL 

There  are  various  kinds  of  fuel  used  in  steam  production,  loca- 
tion, cost,  and  the  exigencies  of  the  case  being  the  deciding  /actors. 
I  sually  the  kind  of  fuel  is  determined  upon,  and  the  boiler  designed 
with  that  end  in  view.  Sometimes,  however,  the  fuel  must  be  adapted 
to  the  boiler. 

Coal.  Coal  is  not  only  the  most  important  fuel,  but  in  many 
localities  the  only  one  available.  It  is  of  vegetable  origir  being  the 


236 


BOILER  ACCESSORIES 


long-decayed  product  of  ancient  forests.  Frequently  it  occurs  so 
mixed  with  earthy  matter  as  to  be  of  little  value;  but  the  supply  of 
good  coal  is  still  abundant,  and  likely  to  be  so  for  some  time  to  come. 

The  most  important  elements  in  coal  are  hydrogen,  producing 
02,000  B.  T.  U.  per  pound,  and  carbon,  producing  14,500  B.  T.  U. 
per  pound.  Although  several  coals  may  have  the  same  total  per- 
centage of  combustible  material  and  ash,  the  heat  values  may  not  be 
the  same,  because  heat  value  depends  upon  the  amounts  of  hydrogen 
and  carbon  they  contain.  The  heat  value  of  fuels  is  determined  by 
chemical  analysis,  or  by  calorimetric  test,  and  varies  for  coal  from 
different  localities.  The  following  table  is  compiled  from  several 
sources : 

ANALYSIS  AND  HEAT  VALUE  OF  VARIOUS  COALS 


POUNDS  OF 

WATER 

KIND  OK  COAL 

PER  CENT 
OF  ASH 

B.  T.  U. 

PER  POUND 

PER  POUND 

(THEORETI- 

CAL) 

Penu.  Anthracite 

,        3.49 

14,1C9 

14.70 

Perm.  Anthracite 

2.90 

14,221 

14.72 

Peun.  Caunel 

15.02 

13,143 

13.60 

Penn.  Couuellsvillc 

6.50 

13,368 

13.84 

Perm.  Semi-bituminous 

10.70 

13,155 

13.62 

Penn.  Brown 

9.50 

12,324 

12.75 

Kentucky  Caking 
Kentucky  Canuel 
Kentucky  Lignite 

2.75 
2.00 
7.00 

14,391 
15,198 
9,326 

14.89 
16.76 
9.65 

Indiana  Caking 

5.  60 

14,146 

14.64 

Indiana  Cannel 

6.00 

13,097 

13.56 

Maryland  Cumberland 

»     13.88 

12,226 

12.65 

Arkansas  Lignite 

5.00 

9,215 

9.54 

Colorado  Lignite 

9.25 

13,562 

,       14.04 

Texas  Lignite 

4.50 

12,962 

13.41 

Washington  Lignite 

3  40 

11,551 

11.  C6 

In  practice,  no  fuel  gives  its  theoretical  evaporation  value.  On 
account  of  several  losses  that  are  inevitably  incurred,  heat  is  radiated 
from,  and  conducted  away  by,  the  boiler  setting.  The  admission  of 
too  much  air  into  the  furnace,  either  through  the  doors  or  through 
cracks  in  the  setting,  reduces  the  theoretical  evaporation  value.  Im- 
proper firing  causes  considerable  loss;  and  errors  in  design,  con- 
struction, or  setting  reduce  the  efficiency. 

The  different  kinds  of  coal  are  too  numerous  to  be  easily  named, 
but  in  general  they  may  be  classified  as  anthracite  or  bituminous,  com- 


£37 


96  BOILER  ACCESSORIES 

monly  called  hard  or  soft  respectively,  of  which  there  are  various  sub- 
divisions. 

Anthracite.  Anthracite  coal  consists  almost  entirely  of  carbon, 
but  has  a  small  amount  of  hydrocarbon.  Good  anthracite  is  lustrous, 
hard,  flinty,  but  breaks  up  easily  under  high  temperature.  It  burns 
with  very  little  flame  and  smoke,  and  gives  an  intense  heat.  It  does 
not  ignite  so  readily  as  the  softer  varieties  of  coal;  but  once  started, 
the  fire  requires  less  attention.  It  is  an  excellent  fuel  where  the  pro- 
duction of  smoke  is  a  decided  objection. 

Semi=Anthracite.  This  is  a  coal  between  pure  anthracite  and 
semi-bituminous.  It  is  not  so  hard  as  anthracite,  and  burns  more 
freely.  It  is  not  so  compact  as  anthracite,  and  burns  with  a  short 
flame,  the  anthracite  having  practically  no  flame. 

Semi=Biturninous.  This  is  the  next  softer  grade  of  coal.  It 
burns  more  freely  than  either  anthracite  or  semi-anthracite,  contains 
more  volatile  hydrocarbon,  and  is  a  valuable  coal  for  steaming  pur- 
poses. 

Bituminous.  Bituminous  coal  forms  by  far  the  larger  portion  of 
steam  coal.  It  contains  a  large  but  varying  amount  of  hyrocarbon  or 
bituminous  matter.  Unless  fired  with  care,  it  will  produce  a  consider- 
able amount  of  smoke  and  clinkers^ 

Dry  Bituminous.  This  is  a  black  coal  with  a  resinous  luster. 
It  burns  freely,  and  kindles  with  much  less  difficulty  than  the  anthra- 
cites. It  is  hard,  but  is  easily  splintered.  When  burning,  it  gives  a 
moderate  amount  of  flame,  with  but  little  smoke,  and  does  not  cake. 
It  is  found  chiefly  in  Maryland  and  Virginia. 

Caking  Bituminous.  This  contains  less  carbon  and  more  hydro- 
carbon than  the  former  class.  It  is  not  so  black;  is  more  resinous; 
and,  under  intense  heat,  readily  forms  into  a  solid,  pasty  mass.  Un- 
less frequently  broken  up,  this  pasty  mass  forms  a  blanket  over  the 
grate,  and  checks  the  draft.  Caking  bituminous  is  a  valuable  coal 
for  the  manufacture  of  gas.  It  is  mined  chiefly  in  the  Mississippi 
valley. 

Cannel.  Cannel  or  long-flame  bituminous  coal  produces  a  con- 
siderable quantity  of  smoke.  It  is  mined  chiefly  in  Pennsylvania, 
Indiana,  and  Missouri;  and  is  a  free-burning  coal,  with  a  strong 
tendency  to  cake.  It  is  largely  used  for  open-grate  purposes. 

Lignite.     Lignite,  or  brown  coal  is  intermediate  between  coal  and 


BOILER  ACCESSORIES  97 

peat.  It  is  made  up  mostly  of  carbon,  with  some  moisture  and 
mineral  matter.  Poor  varieties  are  of  little  value.  Good  lignite 
kindles  with  ease,  and  burns  freely,  but  is  likely  to  contain  a  con- 
siderable amount  of  water,  and  unless  kept  in  a  dry  place  will  absorb 
moisture.  It  is  not  a  very  good  fuel,  but  is  used  in  some  localities 
where  other  varieties  are  more  expensive.  It  comes  largely  from 
Colorado,  Texas,  and  Washington. 

Peat.  This  is  a  form  of  fuel  consisting  of  decayed  roots,  tree- 
trunks,  etc.,  and  earthy  matter.  It  is  found  in  swamps  and  bogs,  and 
has  been  in  process  of  decomposition  a  much  shorter  time  than  any 
of  the  coals.  It  is  cut  out  in  blocks  and  dried.  Peat  has  a  specific 
gravity  of  .4  to  .5,  but  it  can  be  compressed  to  a  much  greater  density. 
It  is  necessary  that  peat  should  be  kept  in  a  dry  place,  for  it  will  readily 
absorb  moisture. 

Coke.  This  is  made  by  driving  o,T  by  heat  the  hydrocarbon  of 
bituminous  or  semi-bituminous  coals.  It  may  be  made  in  gas  retorts, 
as  a  by-prcduct  of  gas  production;  or  it  may  be  made  in  coking  ovens, 
the  gas  being  the  by-product.  The  latter  form  of  coke  is  more  valu- 
able as  a  fuel.  If  the  coal  is  very  moist,  or  if  steam  is  used  in  the  coking 
process,  as  in  the  manufacture  of  water  gas,  the  sulphur  is  burned  out. 
Coke  burns  without  flame;  and,  with  a  free  supply  of  air,  will  make 
an  intensely  hot  fire. 

Charcoal.  Charcoal  is  practically  never  used  for  steam  fuel,  its 
chief  use  being  for  household  or  manufacturing  purposes.  It  is  made 
by  evaporating  the  volatile  matter  from  wood,  either  by  partial  com- 
bustion or  by  heating  in  retorts.  About  50  bushels  of  charcoal  can  be 
obtained  from  a  cord  of  wood. 

Culm.  This  is  a  name  given  to  refuse  dust  at  the  coal  mines, 
sometimes  called  slack.  It  can  be  bought  at  the  mines  at  a  very  low 
rate;  but  the  cost  of  transportation  prohibits  its  use  except  in  the 
immediate  vicinity  of  the  mines.  On  account  of  its  fineness,  it  cannot 
be  burned  in  an  ordinary  grate,  and  is  usually  blown  into  the  boiler 
with  a  sufficient  quantity  of  air,  where  it  burns  somewhat  like  a  gas. 
A  grate  beneath  usually  contains  a  moderate  fire,  which  keeps  the 
culm  well  ignited  and  prevents  the  loss  of  any  particles  that  might 
otherwise  drop  out  of  the  furnace. 

Wood.  There  are  two  principal  divisions  of  wood — hardwood, 
which  is  compact  and  comparatively  heavy,  such  as  oak,  ash,  and 


230 


93  BOILER  ACCESSORIES 

hickory;  and  soft  wood,  which  is  of  soft  and  porous  texture  and  of  less 
specific  gravity,  such  as  pine,  birch,  and  poplar.  Wood  contains 
considerable  moisture,  even  if  left  to  season  in  a  dry  place;  and  after 
being  thoroughly  dried,  it  will  absorb  and  retain  from  10  to  20  per  cent 
of  moisture.  Kiln-dried  wood  contains  nearly  8,000  B.  T.  U.  per 
pound,  while  the  average  wood,  containing  about  25  per  cent  of 
moisture,  has  a  heating  value  of  about  6,000  B.  T.  U. 

The  chemical  composition  of  different  woods  is  nearly  the  same, 
and  pound  for  pound  one  class  of  wood  contains  about  the  same 
heating  value  as  another.  Pine  weighs  about  half  as  much  as  oak 
per  cubic  foot,  and  a  cord  of  such  wood  contains  about  half  the  heating 
value  that  a  cord  of  oak  would  contain. 

Sawdust  and  shavings  are  frequently  used  as  fuel  in  sawmills 
and  planing  mills.  This  kind  of  fuel  is  blown  into  the  furnace  with 
air  from  a  fan,  and  makes  an  intense  heat.  A  fine  grate  at  the  bottom 
collects  the  burning  embers,  which  might  otherwise  drop  into  the  ash- 
pan.  In  mills  where  sawdust  and  shavings  are  used,  they  are  a  by- 
product. 

Straw.  Threshing  machines  through  the  West  use  straw  almost 
entirely  for  fuel.  It  gives  an  intense  heat,  furnishing  5,000  to  6,000 
heat  units  per  pound ;  and  this  is  a  quick  and  easy  way  to  get  rid  of  it. 

Bagasse  is  the  fibrous  portion  of  the  sugar-cane  left  after  the  juice 
has  been  extracted.  In  the  modern  process  of  sugar  manufacture, 
the  cane  is  pressed  so  tightly  that  it  is  ready  for  fuel  without  further 
treating.  Under  favorable  conditions  it  forms  an  excellent  fuel.  The 
pressed  cane  is  a  by-product  which  must  in  some  way  be  got  rid  of. 
It  is  usually  fed  into  the  furnace  through  an  automatic  hopper;  or  it 
may  be  dumped  in  the  fire-room  and  fed  into  the  furnace  by  hand. 
The  furnace  is  constructed  of  brick,  independent  of  the  boilers;  and 
when  bagasse  is  consumed  at  a  high  temperature,  the  oxygen  contained 
in  it  is  nearly  sufficient  to  satisfy  the  carbon  and  hydrogen,  so  that 
little  air  from  the  outside  is  required.  Such  material,  of  course, 
cannot  be  fed  into  an  ordinary  furnace. 

Liquid  Fuels.  These  consist  of  petroleum  and  its  products,  and 
their  use  has  become  quite  extensive  in  the  last  few  years.  The  field 
would  undoubtedly  be  wider  were  there  less  difficulty  in  obtaining  a 
regular  and  constant  supply.  The  greatest  quantities  of  petroleum 
oil  are  produced  in  the  United  States  and  Russia.  Lafge  quantities 


240 


BOILER  ACCESSORIES 


99 


are  found  on  the  Pacific  Coast,  especially  in  Southern  California;  and 
in  that  section  of  the  country,  oil  is  used  as  fuel  to  a  greater  extent 
than  in  the  East,  being  largely  used  on  tugboats,  ferryboats,  and  loco- 
motives. 

The  following,  approximately,  is  the  composition  of  petroleum: 
Carbon  82  to  87  per  cent. 

Hydrogen  11  to  15  per  cent. 

Oxygen  rs¥  to  6  per  cent. 

The  theoretical  heating  power  of  petroleum  is  approximately 
20,000  B.  T.  U.  per  pound,  which  is  nearly  half  as  much  again  as 
that  of  good  coal.  Oil  has  a  further  advantage  over  coal,  in  that  no 
unburned  fuel  necessarily  passes  through  the  furnace,  and  there  is  no 
ash — an  important  item  in  marine  work. 

The  composition  and  specific  gravity  of  petroleums  vary  con- 
siderably, many  of  the  lower  grades  being  unsafe  on  account  of  their 
low  flash-point. 

The  fuel  is  fed  into  the  furnace  through  an  atomizer  operated 
either  by  steam  or  by  compressed  air.  Several  types  of  such  de- 
vices are  shown 
in  Fig.  72.  The 
use  of  the  oil  as  a 
fuel  can  be  readily 
controlled  by  the 
simple  manipula- 
tion of  a  valve;  and 
if  the  fire  is  once 
regulated  to  pro- 
duce the  required 
heat,  it  can  be  kept 
at  that  point  with 
very  little  care. 
The  fire  can  be 
started  with  slight 
trouble,  and  can  be  extinguished  instantly.  The  vaporizing  efficiency 
of  oil  is  much  greater  than  that  of  coal;  and  on  the  Pacific  Coast, 
where  oil  can  be  readily  obtained,  it  is  a  much  more  economical  fuel. 
If  burned  properly,  without  too  heavy  an  ?ir-blast,  there  should  be  no 
production  of  smoke.  A  considerable  saving  may  be  effected  in  the 


C. Chamber  Burner 
Fig.  73.    Types  of  Atomizers  for  Liquid  Fuel. 


S41 


100  BOILER  ACCESSORIES 

fire-room  force,  one  man  being  able  to  operate  several  burners.  There 
is,  of  course,  danger  from  explosion,  on  account  of  vapor  which 
rises  from  the  fuel;  but  if  the  fuel  tank  is  thoroughly  ventilated,  there 
is  little  danger  from  this  source. 

Oil  fuel  may  be  used  to  advantage  in  what  is  called  mixed  firing; 
that  is,  the  oil  may  be  sprayed  onto  the  bed  of  burning  coal.  This 
has  been  condemned  by  many  engineers,  but  it  has  nevertheless  gained 
considerable  headway,  and,  under  proper  conditions,  has  given  satis- 
factory results.  It  is  beyond  the  scope  of  this  work  to  go  minutely 
into  the  subject  of  oil  fuel;  but  for  further  information  the  student  is 
referred  to  the  reports  of  the  Oil  Fuel  Boards  of  the  U.  S.  Navy  and  of 
the  British  Admiralty. 

Gas.  Gas  has  many  advantages  over  any  other  kind  of  fuel. 
There  are  four  different  varieties — natural  gas,  coal  gas,  water  gas, 
and  producer  gas.  Natural  gas  is  used  largely  in  the  vicinity  of  Pitts- 
burg,  Buffalo,  and  some  parts  of  Indiana,  both  for  illuminating  and 
for  steam  purposes.  Where  natural  gas  is  plentiful,  it  is  by  far  the 
cheapest  fuel  that  can  be  used. 

Coal  gas,  made  by  the  distillation  of  coal,  and  water  gas,  obtained 
by  the  decomposition  of  steam  by  incandescent  carbon,  have  been 
used  both  for  lighting  and  for  fuel;  but  in  most  cases  these  gases  may 
be  used  to  greater  economy  directly  in  the  cylinder  of  a  gas  engine 
than  as  fuel  under  a  steam  boiler.  The  same  may  be  said  of  pro- 
ducer gas,  which  is  made  by  blowing  steam  and  air  through  incandes- 
cent coal. 

The  relative  values  of  these  gases  for  evaporation,  are  shown  in 
the  following  table: 

EVAPORATIVE  POWER  OF  GASES 

NATURAL  GAS  COAL  GAS  WATEU  GAS  PRODUCER  GAS 
Cubic  feet  of  p.-is                    1,000               1,000              1,000  1,000 

Pounds  of  water  evap- 
orated 893  591  2G2  115 

Experiments  in  Pittsburg  have  shown  that  1,000  cubic  feet  of 
natural  gas  equals  SO  to  133  pounds  of  coal.  The  coal  used  in  the  com- 
parison varied  from  12,000  to  13,000  B.  T.  U.  per  pound. 

The  Western  Society  of  Engineers  lias  stated  that  one  pound  of 
good  coal  is  equivalent  in  heating  value  to  1\  cu.  ft.  of  natural  gas, 


243 


BOILER  ACCESSORIES  101 


As  in  the  case  of  petroleum,  the  economy  of  burning  gaseous  fuels 
depends  upon  the  locality. 

Artificial  Fuels.  The  waste  of  charcoal,  coal,  sawdust,  etc.,  is 
often  pressed  into  cakes  or  briquettes,  by  means  of  some  adhesive 
mixture,  with  compression.  Wood  tar,  coal  tar,  and  clay  are  used,  ac- 
cording to  convenience.  These  cakes  are  compact,  can  be  stored  in 
small  space,  and  are  used  where  good  fuels  are  difficult  to  obtain. 

STEAM  BOILER  TRIALS 

The  object  of  a  boiler  trial  is  to  determine  the  quantity  and 
quality  of  steam  that  the  boiler  will  supply  under  given  conditions, 
the  horse-power  of  the  boiler,  the  amount  of  fuel  it  takes  to  make  the 
required  steam,  and  its  efficiency. 

The  quantity  of  steam  is  taken  aslhe  amount  of  water  evaporated, 
which,  of  course,  is  the  total  amount  fed  into  the  boiler  during  the  test 
the  water-level  being  the  same  at  the  beginning  and  the  end. 

The  quality  of  the  steam  can  be  determined  by  some  form  of 
calorimeter  already  described;  and  the  efficiency  is  the  ratio  of  the 
heat  units  utilized  in  evaporating  the  water  to  the  total  heat  supplied  to 
the  boiler.  The  heat  utilized  in  evaporation  can  be  found  by  multi- 
plying the  number  of  pounds  of  feed-water  by  the  number  of  heat 
units  required  to  change  the  water  at  the  temperature  of  the  feed  into 
steam  at  gauge  pressure.  The  heat  units  supplied  can  be  determined 
by  carefully  weighing  the  fuel  used  during  the  test,  and  deducting  the 
amount  of  ash  and  unburned  fuel  going  through  the  grates,  with 
proper  allowance  for  moisture,  multiplying  the  result  by  the  total  heat 
of  combustion  of  the  fuel.  The  heat  of  combustion  can  be  obtained 
by  calculation,  or  by  means  of  a  fuel  calorimeter. 

Under  a  short  test  the  boiler  must  be  in  good  working  order  and 
fired  for  some  hours  before  the  beginning  of  the  test,  so  that  the  brick- 
work and  chimney  may  be  thoroughly  heated.  Shortly  before  the 
test  is  begun,  the  fire  may  be  allowed  to  burn  low;  and  by  reducing 
the  amount  of  steam  taken  from  the  boiler,  the  pressure  can  be  kept 
constant.  The  fire  may  then  be  drawn,  the  grate  cleaned,  and  a  new 
fire  quickly  started,  with  wood  and  fresh  coal.  Toward  the  end  of  the 
test  the  fire  may  be  allowed  to  burn  low,  and  at  the  close  may  be  drawn 
and  quenched  with  water,  the  unburned  fuel  being  allowed  for.  In 
a  long  test  of  twenty-four  hours  or  more,  this  is  not  necessary. 


343 


102  BOILER  ACCESSORIES 

If  the  boiler  is  fed  by  a  steam  pump,  the  pump  should  be  run  b} 
steam  taken  from  some  other  boiler,  if  convenient;  if  not,  the  amount 
of  steam  used  by  the  pump  must  be  determined  and  allowed  for.  If 
the  feed-water  is  supplied  by  an  injector,  it  will  take  steam  from  the 
boiler  itself.  About  2  per  cent  of  this  steam  is  consumed  in  forcing  the 
water  into  the  boiler,  the  remainder  going  to  heat  the  feed-water. 

During  the  boiler  trial,  observations  of  temperatures  and  pres- 
sures should  be  made  at  the  same  time,  and  at  about  15-minute  inter- 
vals. In  order  to  obtain  the  result  of  the  test,  the  following  must  be 
known: 

1.  Amount  (in  pounds)  of  coal  burned,  and  number  of  pounds  of  ashes 
left ; 

2.  Number  of  pounds  of  water  pumped  into  boiler; 

3.  Temperature  of  feed- water  when  it  enters  boiler; 

4.  Pressure  of  steam  in  boiler; 

5.  Quality  of  steam  discharged  from  boiler — that  is,  the  per  cent  of 
moisture  in  the  steam. 

The  coal  for  the  furnace  can  be  conveniently  weighed  in  barrels, 
and  may  be  fired  directly  from  these  barrels  or  dumped  on  the  fire- 
room  floor.  The  barrels  should  be  carefully  weighed  when  full  and 
empty,  and  the  time  recorded,  so  that  there  may  be  no  possibility  of 
counting  one  barrel  twice  or  omitting  any.  The  rate  of  combustion 
will  be  fairly  uniform,  and  the  calculations  at  the  times  of  emptying 
the  barrel  will  fairly  indicate  whether  or  not  an  error  has  been  made. 
Any  unburned  coal  should  be  weighed,  and  the  amount  subtracted. 

The  condition  of  the  fire  for  a  twenty-four-hour  test  should  be  the 
same  at  the  beginning  and  the  end.  This  condition  is  estimated  by 
the  eye;  and  unless  great  care  is  used,  an  appreciable  error  is  likely 
to  be  made  If  the  coal  consumption  is  15  to  20  Ibs.  per  square  foot  of 
grate  surface,  an  error  of  two  inches  in  estimating  the  thickness  of  the 
fire  may  cause  an  error  of  as  much  as  2  per  cent  in  the  final  results. 
The  wood  used  in  starting  the  fire  should  be  carefully  weighed, 
and  may  be  considered  as  equal  to  -^  of  the  same  weight  of  coal. 
The  clinker  and  ashes  should  be  carefully  collected  and  weighed,  and 
a  sample  of  the  ashes  examined  to  obtain  the  amount  of  unburned 
fuel. 

There  are  several  ways  of  determining  the  amount  of  water 
pumped  into  the  boiler.  The  best  method  is  to  weigh  it  in  tanks  or 
barrels  set  upon  standard  scales.  There  should  be  two  or  more 


244 


BOILER  ACCESSORIES  103 


barrels  of  sufficient  size,  so  that  the  filling  and  emptying  may  not  be 
hurried.  They  should  be  set  high  enough  to  discharge  readily  into 
the  tank  or  hot  well  from  which  the  feed-water  is  drawn.  The  valves 
should  be  large  and  should  open  quickly,  so  that  the  emptying  may 
not  be  delayed.  If  barrels  are  used, they  should  be  numbered,  and  the 
weight  of  each  accurately  noted,  so  that  there  may  be  no  mistake  in  de- 
ducting the  weight  of  a  barrel  from  the  total  weight  of  barrel  and  water. 
When  one  barrel  is  being  emptied,  the  other  may  be  filled.  The 
weigher  must  use  care  and  intelligence;  otherwise  he  may  become 
confused  in  his  records,  as  in  a  boiler  of  considerable  size  the  barrels 
fill  and  empty  rapidly.  At  the  beginning  of  the  test,  the  level  of  the 
water  in  the  hot  well  should  be  recorded,  and  at  the  end  of  the  test 
should  be  brought  to  the  same  mark.  If  inconvenient  to  weigh  the 
water,  it  may  be  measured  by  a  meter ;  but  if  a  meter  is  used,  it  should  be 
tested  and  its  error  determined  under  like  conditions  of  temperature 
and  pressure.  The  feed-water  should  be  free  from  air,  as  otherwise 
too  large  a  meter  reading  will  be  recorded. 

The  level  in  the  water-glass  of  the  boiler  should  be  carefully  noted 
at  the  beginning  and  end  of  the  test.  If  possible,  the  level  should  be 
constant  throughout  the  test;  and  if  there  is  any  difference  between 
the  beginning  and  the  end,  due  allowance  should  be  made  for  it. 

The  temperature  of  the  feed-water  can  be  taken  best  by  means  of  a 
thermometer  in  a  cup  filled  with  oil  screwed  into  the  feed-pipe  near  the 
check-valve.  If  the  temperature  is  nearly  constant,  readings  at  15- 
minute  intervals  will  suffice;  otherwise  readings  should  be  taken 
every  five  minutes. 

The  steam  pressure  shown  by  the  gauge  should  be  as  nearly  con- 
stant as  possible  throughout  the  test,  and  should  be  practically  the 
same  both  at  the  beginning  and  at  the  end.  Gauge  readings  should  be 
recorded  every  15  minutes,  and  the  fireman  should  see  that  the  pres- 
sure is  constant.  The  gauge  should  be  tested,  and  corrected  if  neces- 
sary. 

Barometric  readings  should  also  be  taken,  two  or  three  being 
sufficient  for  a  ten-hour  run.  These  readings,  in  inches,  may  be  made 
to  indicate  pounds  pressure  by  multiplying  by  .491,  this  being  the 
weight  of  one  cubic  inch  of  mercury.  If  the  trial  is  on  a  vertical  boiler 
which  furnishes  superheated  steam  because  of  the  heat  being  in  con- 
tact with  the  tubes  above  the  water-level,  both  the  pressure-gauge  and 


£45 


104  BOILER  ACCESSORIES 


the  thermometer  should  be  used,  so  that  the  amount  of  superheating 
can  readily  be  found  by  subtracting  the  temperature  due  to  pressure 
(obtained  from  the  steam  tables)  from  the  temperature  readings. 

The  quality  of  steam  can  readily  be  determined  by  a  calorimeter. 
If  there  is  sufficient  steam  space  within  the  boiler,  from  1  to  2  per  cent 
priming  will  generally  result.  If  the  steam  space  is  inadequate,  there 
will  be  more  priming.  If  more  than  2  per  cent  priming  is  present,  the 
steam  will  blow  white  from  the  gauge-cocks  when  opened ;  if  less  than 
2  per  cent,  it  will  appear  blue. 

The  above  observations  are  of  the  more  important  class,  and  must 
be  taken.  In  addition  to  these,  it  is  well  to  take  samples  of  the  flue  gas 
at  intervals  and  from  various  places  in  the  furnac?  or  chimney,  the 
object  being  to  determine-  whether  there  is  a  sufficient  supply  of  air 
admitted,  or  whether  there  is  too  much.  The  draft  of  the  chimney 
may  be  measured  by  means  of  a  U-tube  partially  filled  with  water,  or 
by  a  draft-gauge. 

It  is  well  to  bear  in  mind  that  in  making  the  boiler  test  the  utmost 
care  must  be  used,  both  in  taking  observations  and  in  recording  them, 
and  in  working  up  the  results  of  the  trial.  A  committee  of  the  Ameri- 
can Society  of  Mechanical  Engineers  has  recommended  a  code  of 
rules  for  boiler  trials,  and  the  following  standard  form  for  recording 
results.  These  are  too  voluminous  for  complete  reproduction,  and 
they  can  be  found  in  full  in  Vol.  XXI  of  the  Proceedings  of  the  above 
Society  for  the  year  1900.  The  following  code  of  rules  is  practically 
an  abstract  of  the  above-mentioned  code : 

PRELIMINARIES  TO  A  TEST 

1.  In  preparing  for  and  conducting  trials  of  steam  boilers, 
the  specific  object  of  the  proposed  trial  should  be  clearly  defined  and 
steadily  kept  in  view. 

2.  Measure  and  record  the  dimensions,  position,  etc.,  of  grate 
and  heating  surfaces,  flues,  and  chimneys;  proportion  of  air-space  in 
the  grate-surface;  kind  of  draught,  natural  or  forced. 

3.  Put  the  boiler  in  good  condition.     Have  heating  surface 
clean  inside  and  out;  grate-bars  and  sides  of  furnace  free  from  clinkers; 
dust  and  ashes  removed  from  back  connections;  leaks  in  masonry 
stopped;  and  all  obstructions  to  draught  removed.     See  that  the 
damper  will  open  to  full  extent,  and  that  it  may  be  closed  when  desired. 


243 


BOILER  ACCESSORIES  105 


Test  for  leaks  in  masonry  by  firing  a  little  smoky  fuel  and  immediately 
closing  damper.  The  smoke  will  escape  through  the  leaks  if  there  be 
such. 

4.  Have  an  understanding  with  the  parties  in  whose  interest 
the  test  is  to  be  made,  as  to  the  character  of  the  coal  to  be  used.     The 
coal  must  be  dry;  or,  if  wet,  a  sample  must  be  dried  carefully,  and  a 
determination  of  the  amount  of  moisture  in  the  coal  must  be  made, 
the  calculation  of  the  results  of  the  test  being  corrected  accordingly. 
Wherever  possible,  the  test  should  be  made  with  standard  coal  of  a 
known  quality,     For  that  portion  of  the  country  east  of  the  Alleghany 
mountains,  good  anthracite  egg  coal  or  Cumberland  semi-bituminous 
coal  may  be  taken  as  the  standard  for  making  tests.     West  of  the 
Alleghany  mountains  and  east  of  the  Missouri  river,  Pittsburg  lump 
coal  may  be  used. 

In  all  important  tests,  a  sample  of  coal  should  be  selected  for 
chemical  analysis. 

5.  Establish  the  correctness  of  all  apparatus  used  in  the  test 
for  weighing  and  measuring.     These  are:  1.     Scales  for  weighing 
coal,  ashes,  and  water.     2.     Tanks  or  water-meters  for  measuring 
water.     Water-meters,  as  a  rule,  should  only  be  used  as  a  check  on 
other  measurements.     For  accurate  work  the  water  should  be  weighed 
or  measured  in  a  tank.     3.    Thermometers  and  pyrometers  for  taking 
temperatures  of  air,  steam,  feed -water,  waste  gases,  etc.    4.    Pressure- 
gauges,  draft-gauges,  etc. 

6.  Before  beginning  a  test,  the  boiler  and  chimney  should  be 
thoroughly  heated  to  their  usual  working  temperature.     If  the  boiler 
is  new,  it  should  be  in  continuous  use  at  least  a  week  before  testing,  so 
as  to  dry  the  mortar  thoroughly  and  heat  the  walls. 

7.  Before  beginning  a  test,  the  boiler  and  connections  should 
be  free  from  leaks;  and  all  water  connections,  including  blow  and 
extra  feed-pipes,  should  be  disconnected  or  stopped  with  blank  flanges, 
except  the  particular  pipe  through  which  water  is  to  be  fed  to  the 
boiler  during  the  trial.     In  locations  where  the  reliability  of  the  power 
is  so  important  that  an  extra  feed-pipe  must  be  kept  in  position,  and  in 
general  when,  for  any  other  reason,  water-pipes  other  than  the  feed- 
pipes cannot  be  disconnected,  such  pipes  may  be  drilled  so  as  to  leave 
openings  in  their  lower  sides,  which  should  be  kept  open  throughout 
the  test  as  a  means  of  detecting  leaks  or  accidental  or  unauthorized 


247 


100  BOILER  ACCESSORIES 

opening  of  valves.  During  the  test  the  blow-off  pipe  should  remain 
exposed. 

If  an  injector  is  used  it  must  receive  steam  directly  from  the  boiler 
being  tested,  and  not  from  a  steam-pipe  or  from  any  other  boiler. 

See  that  the  steam  pipe  is  so  arranged  that  water  of  condensation 
cannot  run  back  into  the  boiler.  If  the  steam  pipe  has  such  an  inclina- 
tion that  the  water  of  condensation  from  any  portion  of  the  steam  - 
pipe  system  may  run  back  into  the  boiler,  it  must  be  trapped  so  as  to 
prevent  this  water  getting  into  the  boiler  without  being  measured. 

8.  A  test  should  last  at  least  ten  hours  of  continuous  running, 
and  twenty-four  hours  whenever  practicable. 

9.  The  conditions  of  the  boiler  and  furnace  in  all  respects 
should  be,  as  nearly  as  possible,  the  same  at  the  end  as  at  the  beginning 
of  the  test.     The  steam  pressure  should  be  the  same,  the  water-level 
the  same,  the  fire  upon  the  grates  should  be  the  same  in  quantity  and 
condition,  and  the  walls,  flues,  etc.,  should  be  of  the  same  temperature. 
To  secure  as  near  an  approximation  to  exact  uniformity  as  possible 
in  conditions  of  the  fire  and  in  temperatures  of  the  walls  and  flues, 
the  following  method  of  starting   and    stopping  a    test   should   be 
adopted. 

10.  Standard    Method.     Steam  being  raised   to   the   working 
pressure,  remove  rapidly  all  the  fire  from  the  grate,  close  the  damper, 
clean  the  ash-pit,  and  as  quickly  as  possible  start  a  new  fire  with 
weighed  wood  and  coal,  noting  the  time  of  starting  the  test  and  the 
height  of  the  water-level  while  the  water  is  in  a  quiescent  state,  just 
before  lighting  the  fire. 

At  the  end  of  the  test,  remove  the  whole  fire,  clean  the  grates  and 
ash-pit,  and  note  the  water-level  when  the  water  is  in  a  quiescent 
state;  record  the  time  of  hauling  the  fire  as  the  end  of  the  test.  The 
water-level  should  be  as  nearly  as  possible  the  same  as  at  the  beginning 
of  the  test.  If  it  is  not  the  same,  a  correction  should  be  made  by  com- 
putation, and  not  by  operating  pump  after  test  is  completed.  It  wil 
generally  be  necessary  for  a  time  to  regulate  the  discharge  of  steam 
from  the  boiler  tested,  by  means  of  the  stop-valve,  while  fires  are  being 
hauled  at  the  beginning  and  at  the  end  of  the  test,  in  order  to  keep 
the  steam  pressure  in  the  boiler  at  those  times  up  to  the  average  during 
the  test. 

11.  Alternate  Method.     Instead  of  the  Standard  method  above 


248 


BOILER  ACCESSORIES  107. 


described,  the  following  may  be  employed  where  local  conditions 
render  it  necessary : 

At  the  regular  time  for  slicing  and  cleaning  fires,  have  them 
burned  rather  low,  as  is  usual  before  cleaning,  and  then  thoroughly 
cleaned ;  note  the  amount  of  coal  left  on  the  grate  as  nearly  as  it  can 
be  estimated ;  note  the  pressure  of  steam  and  the  height  of  the  water- 
level — which  should  be  at  the  medium  height  to  be  carried  throughout 
the  test — at  the  same  time;  and  note  this  time  as  the  time  of  starting 
the  test.  Fresh  coal,  which  has  been  weighed,  should  now  be  fired. 
The  ash-pits  should  be  thoroughly  cleaned  at  once  after  starting. 
Before  the  end  of  the  test  the  fires  should  be  burned  low-,  just  as  before 
the  start,  and  the  fires  cleaned  in  such  a  manner  as  to  leave  the  same 
amount  of  fire,  and  in  the  same  condition,  on  the  grates  as  at  the  start. 
The  water-level  and  steam  pressure  should  be  brought  to  the  same 
point  as  at  the  start,  and  the  time  of  the  ending  of  the  test  should  be 
noted  just  before  fresh  coal  is  fired. 

12o  Keep  the  Conditions  Uniform.  The  boiler  should  be  run 
continuously,  without  stopping  for  meal-times  or  for  rise  or  fall  of 
pressure  of  steam  due  to  change  of  demand  for  steam.  The  draught, 
being  adjusted  to  the  rate  of  evaporation  or  combustion  desired  before 
the  test  is  begun,  should  be  retained  constant  during  the  test,  by 
means  of  the  damper. 

If  the  boiler  is  not  connected  to  the  same  steam  pipe  with  other 
boilers,  an  extra  outlet  for  steam  with  valve  in  same  should  be  pro- 
vided, so  that  in  case  the  pressure  should  rise  to  that  at  which  the 
safety-valve  is  set,  it  may  be  reduced  to  the  desired  point  by  opening 
the  extra  outlet,  without  checking  the  fires. 

If  the  boiler  is  connected  to  a  main  steam  pipe  with  other  boilers, 
the  safety-valve  on  the  boiler  being  tested  should  be  set  a  few  pounds 
higher  than  those  of  the  other  boilers,  so  that  in  case  of  a  rise  in  pres- 
sure the  other  boilers  may  blow  off,  and  the  pressure  be  reduced  by 
closing  their  dampers,  allowing  the  damper  of  the  boiler  being  tested 
to  remain  open,  and  firing  as  usual. 

All  the  conditions  should  be  kept  as  nearly  uniform  as  possible, 
such  as  force  of  draught,  pressure  of  steam,  and  height  of  water.  The 
time  of  cleaning  the  fires  will  depend  upon  the  character  of  the  fuel, 
the  rapidity  of  combustion,  and  the  kind  of  grates.  When  very  good 
coal  is  used,  and  the  combustion  not  too  rapid,  a  ten-hour  test  may  be 


243 


108  BOILEil  ACCESSORIES 

run  without  any  cleaning  of  the  grates  other  than  just  before  the 
beginning  and  just  before  the  end  of  the  test.  But  in  case  the  grates 
have  to  be  cleaned  during  the  test,  the  intervals  between  one  cleaning 
and  another  should  be  uniform. 

13.  Keeping  the  Records.    The  coal  should  be  weighed  and 
delivered  to  the  fireman  in  equal  portions,  each  sufficient  for  about 
one  hour's  run;  and  a  fresh  portion  should  not  be  delivered  until  the 
previous  one  has  all  been  fired.     The  time  required  to  consume  each 
portion  should  be  noted,  the  time  being  recorded  at  the  instant  of 
firing  'the  first  of  each  new  portion.     It  is  desirable  that  at  the  same 
time  the  amount  of  water  fed  into  the  boiler  be  accurately  noted  and 
recorded,  including  the  height  of  the  water  in  the  boiler  and  the 
average  pressure  of  steam  and  temperature  of  feed  during  the  time. 
By  thus  recording  the  amount  of  water  evaporated  by  successive 
portions  of  coal,  the  record  of  the  test  may  be  divided  into  several 
divisions,  if  desired,  at  the  end  of  the  test,  to  discover  the  degree  of 
uniformity   of  combustion,  evaporation,  and  economy  at  different 
stages  of  the  test. 

14.  Priming  Tests.    In  all  tests  in  which  accuracy  of  results  is 
important,  calorimeter  tests  should  be  made  of  the  percentage  of 
moisture  in  the  steam,  or  of  the  degree  of  superheating.     At  least 
ten  such  tests  should  be  made  during  the  trial  of  the  boiler,  or  so  many 
as  to  reduce  the  probable  average  error  to  less  than  one  per  cent; 
and  the  final  records  of  the  boiler  test  should  be  corrected  according 
to  the  average  results  of  the  calorimeter  tests. 

On  account  of  the  difficulty  of  securing  accuracy  in  these  tests, 
the  greatest  care  should  be  taken  in  the  measurements  of  weights  and 
temperatures.  The  thermometers  should  be  accurate  within  a  tenth 
of  a  degree;  and  the  scales  on  which  the  water  is  weighed,  to  within 
one-hundredth  of  a  pound. 

15.  As  each  fresh  portion  of  coal  is  taken  from  the  coal-pocket, 
a  representative  shovelful  should  be  selected  from  it  and  placed  in  a 
barrel  or  box,  to  be  kept  until  the  end  of  the  trial,  for  analysis.    The 
samples  should  then  be  thoroughly  mixed  and  broken.     This  sample 
should  be  put  in  a  pile,  and  carefully  quartered.     One  quarter  may 
then  be  put  in  another  pile,  and  the  process  repeated  until  five  or  six 
pounds  remain.     One  portion  of  this  sample  is  to  be  used  for  the 


250 


I1 


pi 

K   •   ® 

155 

BSd 
1S1 

eli 


HOILER  ACCESSORIES  109 

determination  of  the  moisture  and  heating  value;  the  other,  for  chemi- 
cal analysis. 

16.  The  ashes  refuse  should  be  weighed  dry,  and  a  sample 
frequently  taken  to  show  the  amount  of  combustible  material  passing 
through  the  grate.     To  get  a  representative  ash  sample,  the  ash-pile 
should  be  quartered  as  required  for  the  coal. 

17.  The  quality  of  the  fuel  should  be  determined  by  heat  test,  by 
analysis,  or  by  both. 

18.  The  analysis  of  the  flue  gases  is  an  especially  valuable 
method  of  determining  the  relative  value  of  different  methods  of 
firing  or  of  different  kinds  of  furnaces.     Great  care  shoul^l  be  taken 
to  procure  average  samples,  since  the  combustion  of  the  gases  may 
vary  at  different  points  in  the  flue;  and  as  the  combustion  of  flue  gas 
is  liable  to  vary  from  minute  to  minute,  the  sample  of  gas  should  be 
drawn  through  a  considerable  period  of  time. 

19.  It  is  desirable  to  have  a  uniform  system  of  determining  and 
recording  the  quantity  of  smoke  produced.     This  is  usually  expressed 
in  percentages,  depending  upon  the  judgment  of  the  observer. 

20.  In  tests  for  the  purpose  of  scientific  research  in  which  the 
determination  of  all  variables  is  desirable,  certain  observations  should 
be  made  which  in  general  are  not  necessary  —  such  as  the  measure- 
ment of  air-supply,  the  determination  of  its  moisture,  the  determina- 
tion of  the  heat  loss  by  radiation,  the  infiltration  of  air  through  the 
setting,  etc.  —  but  as  these  determinations  are  rarely  undertaken,  no 
definite  instructions  are  here  given. 

21.  Two  methods  of  defining  "and   calculating  the  efficiency  of 
the  boiler  are  recommended.     They  are: 

Heat    absorbed   per  pound   of  combustible 
(I)    Efficiency  of   the  boiler^       -——  --_  polincrof  combustible 


Heat  absorbed  per  pound  of  coal 
(2)    Efficiency  of    boder  and  - 


The  first  of  these  is  the  one  usually  adopted. 

22.  An  approximate  statement  of  the  distribution  of  the  heating 
value  of  the  coal  among  the  several  items  of  heat  utilized,  may  be 
included  in  the  report  of  a  test  when  analyses  of  the  fuel  and  chimney 
gases  have  been  made. 

23.  Record  of  the  Test.    The  data  and  results  of  the  trial 
should  be  recorded  in  a  systematic  manner,  according  either  to  Table  1 


251 


110  BOILER  ACCESSORIES 

(see  Vol.  XXI,  Transactions  of  the  American  Society  of  Mechanical 
Engineers),  or  Table  2,  taken  from  those  "Transactions." 

TABLE  2 
Data  and  Results  of  Evaporative  Test 

Arranged  in  accordance  with  the  short  form  advised  by  the  Boiler  Test  Committee 
of  the  American  Society  of  Mechanical  Engineers,  Code  of  1899: 
Made  by on boiler,  at 

To  determine 

Kind  of  fuel 

Kind  of  furnace 

Method  of    starting  and   stopping  the  test    (Standard  or  Alternate,  Arts.  X 

and  XI,  Code) 

Grate  surface sq.  ft. 

Water-heating  surface "     " 

Superheating  surface "    " 

Total  Quantities 

1.  Date  of  Trial 

2.  Duration  of  Trial hours 

3.  Weight  of  coal  as  fired Ibs. 

4.  Percentage  of  moisture  in  coal per  cent 

5.  Total  weight  of  dry  coai  consumed Ibs. 

G.  Total  ash  and  refuse " 

7.  Percentage  of  ash  and  refuse  in  dry^coal per  cent 

8.  Total  weight  of  water  fed  to  boiler Ibs. 

9.  Water  actually  evaporated,  corrected    for  moisture  or 

superheat  in  steam " . 

10.  Equivalent  water   evaporated  into  dry  steam  from  and 

at  212° F... " 

Hourly  Quantities 

11.  Dry  coal  consumed  per  hour. Ibs. 

12.  Dry  coal  per  square  foot  of  grate  surface  per 

hour " 

13.  Water    evaporated    per    hour    corrected    for 

quality  of  steam " 

14.  Equivalent   evaporation   per   hour    from    and 

at  212*  F " 

15.  Equivalent  evaporation  per  hour  from  and  at 

212°  F.  per  square    foot   of    water-heating 
surface " 

Average  Pressures,  Temperatures,  Etc 

16.  Steam  pressure  by  gauge Ibs.  per  sq.  in. 

17.  Temperature  of  feed-water  entering  boiler degrees 

18.  Temperature  of  escaping  gases  from  boiler 

19.  Force  of  draught  between  damper  and  boiler.  .  .     ins.  of  water 

20.  Percentage  of  moisture  in  steam,  or  number  or 

degrees  of  superheating per  cent  or  degrees 

i 


25ft 


BOILER  ACCESSORIES 


111 


Horse=Power 

21.  Horse-power  developed  (item  It  ~  314) H.  P. 

22.  Builder's  rated  horse-power " 

23.  Pereentage  of  builder's  rated  horse-power  developed  .  .  .per  rent. 

Economic  Results 

24.  Water  apparently  evaporated  under  actual  conditions  per 

pound  of  coal  as  fired  (item  8  +  item  3) lbs. 

25.  Equivalent    evaporation    from    and    at     212°    F.   per  pound 

•  of  coal  as  fired  (item  10  H-  item  3) " 

26.  Equivalent  evaporation    from  and  at   212°  F.  per  pound  of 

dry  coal  (item  10  -f-  item  5) " 

27.  Equivalent  evaporation    from    and  at   212°  F.  per  pound  of 

combustible  [item  10  ~  (item  5  —  item  f>)] " 

If  items  25,  26,  and  27  are  not  corrected  for  quality  of  steam,  the  fact  should  be 
stated. 

Efficiency 

28.  Calorific  value  of  the  dry  coal  per  pound .  .B.  T.  I'. 

29.  Calorific  value  of  the  combustible  per  pound " 

30.  Efficiency  of  boiler  (based  on  combustible) per  cent. 

31.  Efficiency  of  boiler,  including  grate  (based  on  dry  coal)        " 

Cost  of  Evaporation 

32.  Cost  of  coal  per  ton  of lbs.  delivered  in  boiler-room     $ 

33.  Cost  of  coal  required  for  evaporating   1.000  lbs.  of  water 

from  and  at  212°  F 

A  log  of  the  test  should  be  kept  on  properly  prepared  blanks 
containing  headings  as  follows: 


PRESSURES 

TEMPERATURES 

FUEL 

FEED-WATEH 

S 

bC 

M 

a 

Vl 

d 

TfME 

Baromete 

Steam  gai 

Draft  gau 

3 

M 

W 

Boiler-roo 

3 

s 

Feed-wate 

g 
| 
(5) 

S 
H 

Pounds 

X 
H 

s 
o 

s 

J 

FIRING 

Starting  the  Fire.  The  fireman  should  first  ascertain  the  water- 
level;  as  the  gauge-glass  is  not  always  reliable,  on  account  of  im- 
purities, foam,  etc.,  the  gauge-cocks  should  be  tried.  In  a  battery 


253 


112  BOILER  ACCESSORIES 


of  boilers,  the  gauge-cocks  of  each  should  be  opened,  for  the  water 
may  not  stand  at  the  same  level  in  each.  The  safety-valve  should  be 
raised  slightly  from  its  seat.  If  the  fire  has  been  banked  over  night, 
open  the  draughts,  and  rattle  down  the  ashes  and  clinkers  from  the 
grate.  In  case  the  fire  has  been  allowed  to  go  out,  a  new  one  may  be 
started  if  the  gauge-glass  shows  the  proper  amount  of  water,  and  the 
valves  work  well. 

If  anthracite  coal  is  used,  first  throw  a  thin  layer  of  coal  all  over 
the  grate,  then  place  a  piece  of  wood  across  the  mouth  of  the  furnace 
just  inside  the  door  and  lay  other  pieces  of  wood  at  right  angles  to 
the  cross-piece  with  the  ends  resting  on  it.  This  allows  a  space  under 
the  wood  for  air.  Now  throw  on  coal  until  the  wood  is  covered.  The 
fire  may  be  started  with  oily  cotton  waste,  shavings,  or  any  combustible 
material. 

Keep  the  furnace  door  open  and  the  draught-plate  closed  until 
the  wood  is  burning  freely,  which  causes  the  flame  to  pass  over  and 
through  the  coal  and  to  ignite  it.  The  fire  is  then  spread  or  pushed 
back  evenly  over  the  furnace  bars;  the  furnace  door  closed;  the  ash- 
pit door  opened,  as  the  draught  requires;  and  more  coal  added  when 
necessary,  If  bituminous  coal  is  used,  do  not  spread  a  thin  layer  over 
the  grate  bars  imrl?r  the  wood. 

Tho  fire  at  the  srtart  should  be  slow,  to  cause  gradual,  uniform 
heating  of  the  water  and  various  parts  of  the  boiler.  If  steam  is 
raised  too  rapidly,  enormous  strains  are  set  up,  due  to  unequal  expan- 
sion, thereby  causing  leakage  at  joints,  and  perhaps  rupture. 

If  the  boiler  is  of  the  water-tube  type,  steam  may  be  raised  more 
rapidly,  because  the  amount  of  water  is  less  and  the  joints  are  usually 
placed  at  some  distance  from  the  intense  heat  of  the  fire. 

The  fire  being  started,  the  method  of  adding  coal  depends  upon 
the  fireman,  the  kind  of  coal,  the  type  of  boiler,  and  the  rate  of  com- 
bustion. There  are  three  general  methods  of  firing — spreading, 
alternate  or  side  firing,  and  coking. 

Spreading  is  accomplished  by  placing  small  amounts  of  coal 
uniformly  over  the  entire  surface  of  the  grate  at  short  intervals.  By 
this  method,  the  coal  is  thrown  just  where  it  is  wanted  and  then  not 
disturbed.  The  fire  should  be  hollowed  in  the  center;  that  is,  it 
should  be  thicker  at  the  sides.  Good  results  are  obtained  from  this 
method,  since  the  fire  can  be  kept  in  the  right  condition  at  all  times, 


254 


BOILER  ACCESSORIES  113 

if  the  coal  is  of  the  right  sort.  During  the  operation  of  firing,  the 
door  should  be  kept  open  as  little  as  possible,  or  the  h're  will  be  cooled 
by  the  entrance  of  cold  air.  For  a  short  time,  while  the  coal  is  givin^ 
off  gas,  the  draught-plate  of  the  furnace  door  should  be  opened,  in 
order  that  sufficient  air  may  be  admitted  above  the  coal  to  burn  the 
hydrocarbons. 

When  the  alternate  or  side  firing  method  is  used,  coal  is  spread 
so  as  to  cover  one  side  of  the  fire  completely  at  one  firing,  leaving  the 
other  side  bright.  At  the  next  firing,  the  bright  side  is  covered.  The 
hydrocarbons  given  off  by  the  fresh  coal  are  burned  by  the  hot  gases 
from  the  incandescent  coal.  This  method  is  superior  to  spreading; 
because  the  entire  furnace  is  not  cooled  off  by  the  addition  of  fresh 
fuel. 

Side  firing  is  most  advantageous  with  two  furnaces  leading  to 
a  common  combustion  chamber.  The  furnaces  are  fired  at  regular 
intervals  with  moderate  charges  of  coal,  and  the  draught-plates  are 
opened  while  the  coal  is  giving  off  gas. 

The  two  systems  described  above  are  best  adapted  to  anthracite 
coal,  since  it  burns  with  comparatively  little  smoke. 

With  bituminous  coal,  which  is  soft  and  burns  with  considerable 
smoke,  the  coking  method  is  used.  The  coal  is  piled  on  the  grate  just 
inside  the  door,  and  allowed  to  coke  from  1*5  to  30  minutes.  During 
this  time,  the  hydrocarbons  are  driven  off  and  burned  by  the  heat 
from  the  fire.  In  order  fully  to  accomplish  this,  air  must  be  admitted 
above  the  grate  through  the  draught-plates  of  the  furnace  door. 
The  coke  is  then  pushed  backward  over  the  fire,  and  a  new  supply 
placed  on  the  front  of  the  grate.  The  air  admitted  prevents  the  form- 
ing of  carbon  monoxide  gas  and  smoke.  At  the  same  time,  however,  it 
cools  the  furnace  somewhat  and  reduces  the  rate  of  evaporation;  but 
this  objection  is  not  serious  unless  a  boiler  must  be  worked  to  its  maxi- 
mum capacity  in  order  to  furnish  the  required  amount  of  steam.  If 
this  is  the  case,  economy  is  sacrificed  to  rapidity,  for  a  low  rate  of 
combustion  is  usually  more  economical  than  a  high  rate. 

The  necessary  thickness  of  a  bed  for  the  best  results,  is  found  by 
experiment.  It  depends  on  the  draught  and  the  kind  of  coal  used. 
It  the  former  is  strong,  and  the  coal  in  large  lumps,  the  bed  may  be 
thick  (about  one  foot);  but  if  the  draught  is  weak,  or  if  the  coal  is 
small,  the  bed  must  be  thin  (about  three  or  four  inches),  so  that  suffi- 


255 


Ill  BOILER  ACCESSORIES 

cient  air  may  pass  through.  In  marine  and  locomotive  work,  with 
forced  draught,  the  bed  must  be  very  thick  to  get  a  large  coal  con- 
sumption per  square  foot  per  hour.  With  the  same  draught,  bitu- 
minous coal  can  be  fired  more  thickly  than  anthracite,, 

After  finding  from  experiment  the  best  thickness  for  the  bed,  keep 
it  at  that  thickness.  Always  keep  the  bed  of  uniform  thickness,  and 
never  let  the  fire  burn  holes  in  the  bed,  and  do  not  let  the  rear  of  the 
grate  become  bare.  If  a  larger  amount  of  steam  is  required,  fire 
smaller  quantities  at  more  frequent  intervals.  Do  not  fire  a  large 
amount  of  coal,  and  wait  for  the  pressure  to  rise.  The  firing  of  fresh 
coal  chills  the  furnace  and  temporarily  retards  combustion.  The 
coal  should  be  fired  in  small  quantities  and  as  quickly  as  possible. 
Keep  the  fire  free  from  ashes  and  clinkers,  but  do  not  clean  the  fires 
oftener  than  is  necessary. 

Four  tools  are  used  for  cleaning  the  fire — the  slice-bar',  the  prick- 
bar;  the  clinker  hook.,  sometimes  called  the  devil's  claw;  and  the  hoe 
or  rake. 

The  slice-bar  is  a  long,  straight  bar,  with  the  end  flattened.  It 
is  used  to  break  up  clinkers  by  thrusting  it  between  the  grate  and  the 
fire.  It  is  also  used  to  break  up  caking  coaL  The  prick-bar  is  similar 
to  the  slice-bar,  except  that  the  end  is  bent  at  right  angles  like  a  hook. 
To  remove  ashes,  the  prick-bar  is  run  along,  up  between  the  grate 
bars,  from  underneath.  This  bar  is  often  made  with  detachable  hook, 
so  that  the  end  may  be  replaced  when  burned  off.  The  clinker  hook, 
or  devil's  claw,  is  used  to  haul  the  fire  forward.  The  hoe,  or  rake,  is 
used  to  draw  out  cinders,  to  haul  the  fire  forward,  etc. 

In  cleaning  the  fire,  the  fireman  first  looks  to  the  water-and  steam. 
There  should  be  enough  water  and  sufficient  steam  pressure  to  last 
during  cleaning.  Then  he  breaks  up  the  clinkers  with  the  slice-bar, 
and  removes  the  ashes  with  the  prick-bar.  If  necessary,  he  pushes  the 
fire  to  the  rear,  thoroughly  cleans  the  front  of  the  grate  bars,  and  then 
hauls  it  forward  and  cleans  the  back  of  the  furnace  bars.  Some  fire- 
men clean  one  side  at  a  time,  instead  of  first  the  front  and  then  the 
rear.  The  fire  should  be  allowed  to  burn  down  before  cleaning;  but 
sufficient  fuel,  called  chaff,  should  be  left  to  start  the  fire  quickly. 
Before  cleaning,  partly  close  the  dampers,  so  that  the  amount  of  cold  air 
admitted  will  be  small.  For  this  reason  and  to  prevent  loss  of  pressure, 
clean  as  rapidly  as  possible. 


£56 


BOILER  ACCESSORIES  115 


Banking  the  fire  depends  upon  the  condition  of  the  fire,  the 
fireman  himself,  and  the  length  of  time  it  is  to  remain  banked.  First 
clean  and  place  all  the  coal  in  a  small  space  at  the  bridge ;  then  cover 
with  fresh  coal  to  a  depth  depending  on  the  length  of  time  the  fire 
is  to  remain  banked.  Then  close  all  dampers  and  open  the  door. 
Some  firemen  cover  the  front  of  the  furnace  bars  with  ashes. 

To  start  from  a  banked  fire,  first  examine  the  condition  of  the 
water-level,  steam  pressure,  safety-valves,  etc.  Then  clean  the  fire 
with  the  slice-bar,  and  rattle  down  the  ashes  with  the  prick-bar.  After 
spreading  the  coal  evenly  over  the  grate,  cover  with  a  thin  layer  of  coal, 
and  open  the  dampers. 

CARE  OF  BOILERS 

Any  amount  of  time  spent  in  the  proper  care  of  a  steam  boiler 
will  be  amply  repaid,  for  this  is  of  great  importance.  The  boiler,  of 
course,  should  be  so  designed  and  constructed  that  all  parts  can  be 
inspected  readily;  but  this  is  of  little  benefit  unless  proper  and  rigid 
inspections  are  made.  All  internal  fittings,  such  as  fusible  plugs, 
water  alarms,  feed-pipes,  and  the  like,  should  occasionally  be  examined 
to  see  if  they  are  tight  and  in  good  working  order.  If  due  care  is  not 
given  to  the  boiler,  its  life  will  be  materially  shortened. 

The  following  rules  for  the  management  and  care  of  boilers  have 
been  established  by  the  Hartford  Steam  Boiler  Inspection  &  Insur- 
ance Company,  and  should  be  carefully  followed,  whether  the  boiler 
is  insured  by  the  above-mentioned  company  or  not: 

1.  Condition  of  Water.    The  first  duty  of  an  engineer,  when  he 
enters  his  boiler-room  in  the  morning,  is  to  ascertain  how  many  gauges 
of  water  there  are  in  his  boilers.     Never  unbank  or  replenish  the  fires 
until  this  is  done.     Accidents  have  occurred,  and  many  boilers  have 
been  entirely  ruined  from  neglect  of  this  precaution. 

2.  Low  Water.     In  case  of  low  water,  cover  the  fires  immedi- 
ately with  ashes;  or,  if  no  ashes  are  at  hand,  use  fresh  coal,  and  close 
ash-pit  doors.     Do  not  turn  on  the  feed  under  any  circumstances,  nor 
tamper  with  or  open  the  safety-valve.     Let  the  steam  outlets  remain 
as  they  are. 

3.  In  Case  of  Foaming.     Close  throttle,  and  keep  closed  long 
enough  to  show  true  level  of  water.     If  that  level  is  sufficiently  high, 
feeding  and  blowing  will  usually  suffice  to  correct  the  evil.     In  case 


257 


110  BOILER  ACCESSORIES 

of  violent  foaming,  caused  by  dirty  water  or  by  change  from  salt  to 
fresh  water  or  vice  versa,  in  addition  to  the  action  above  stated,  check 
draught,  and  cover  fires  with  fresh  coal. 

4.  Leaks.     When   leaks  are  discovered,   they   should   be   re- 
paired as  soon  as  possible. 

5.  Blowing  Off.     Clean  furnace  and  bridge  wall  of  all  coal  and 
ashes.     Allow  brickwork  to  cool  down  for  two  hours  at  least  before 
opening  blow-off.     A  pressure  exceeding  20  Ibs.  should  not  be  allowed 
when  boilers  are  blown  out.     Blow  out  at  least  once  in  two  weeks. 
In  case  the  feed  becomes  muddy,  blow  out  six  or  eight  inches  every 
day.     When  surface  blow-cocks  are  used,  they  should  be  frequently 
opened' for  a  few  minutes  at  a  time. 

(>.  Filling  Up  the  Boiler.  After  blowing  down,  allow  the 
boiler  to  become  cool  before  filling  again.  Cold  water  pumped  into 
hot  boilers  is  very  injurious,  from  the  sudden  contraction  set  up. 

7.  Exterior  of  Boiler.     Care  should  be  taken  that  no  water 
comes  in  contact  with  the  exterior  of  the  boiler,  either  from  leaky 
joints  or  from  other  causes. 

8.  Removing  Deposit  and  Sediment.     In  tubular  boilers,  the 
handholes    should  be  frequently  opened,  all  collections  removed,  and 
fore-plates  carefully  cleaned.     Also,  when  boilers  are  fed  in  front  and 
blown  off  through  the  same  pipe,  the  collection  of  mud  or  sediment  in 
the  rear  end  should  be  removed  frequently. 

9.  Safety= Valves.     Raise    the    safety-valves    cautiously    and 
frequently,  as  they  are  liable  to  become  fast  in  their  seats  and  useless 
for  the  purpose  intended. 

10.  Safety= Valve  and  Pressure=Gauge.     Should  the  gauge  at  any 
time  indicate    the    limit    of    pressure    allowed    by    the    insurance 
company,  see  that  the  safety-valves  are  blowing  off.     In  case  of  dif- 
ference, notify  the  company's  inspector. 

11.  Gauge=Cocks,  Glass  Gauge.    Keep  gauge-cocks  clear  and 
in  constant  use.     Glass  gauges  should  not  be  relied  on  altogether. 

12.  Blisters.     When  a  blister  appears,  there  must  be  no  delay 
in  having  it  carefully  examined  and  trimmed  or  patched,  as  the  case 
may  require. 

13.  Clean  Sheets.     Particular  care  should  be  taken  to  keep 
sheets  and  parts  of  boilers  exposed  to  the  fire,  perfectly  clean;  also 


858 


BOILER  ACCESSORIES  117 

all  tubes,  flues,  and  connections  well  swept.     This  is  particularly 
necessary  where  wood  or  soft  coal  is  used  for  fuel. 

14.  General  Care  of  Boilers  and  Connections.     Under  all  cir- 
cumstances, keep  the  gauges,  cocks,  etc.,  clean  and  in  good  order,  and 
things  generally  in  and  about  the  engine-room  in  a  neat  condition. 

15.  Getting   Up  Steam.     In  preparing  to  get  up  steam  after 
boilers  have  been  open  or  out  of  service,  great  care  should  be  exercised 
in  making  the  manhole  and  handhole  joints.     Safety-valve  should 
then  be  opened  and  blocked  open,  and  the  necessary  supply  of  water 
run  in  or  pumped  into  the  boilers,  until  it  shows  at  second  gauge  in 
tubular  and  locomotive  boilers;  a  higher  level  is  advisable  in  vertical 
tubulars  as  a  protection  to  tlte  top  ends  of  tubes.     After  this  is  done, 
fuel  may  be  placed  upon  the  grate,  dampers  opened,  and  fires  started. 
If  chimney  or  stack  is  cold  and  does  not  draw  properly,  burn  some 
oily  waste  or  light  kindling  at  the  base.     Start  (ires  in  ample  time,  so 
that  it  will  not  be  necessary  to  urge  them  unduly.     When  steam 
issues  from  the  safety-valve,  lower  it  carefully  to  its  seat  and  note 
pressure  and  behavior  of  steam-gauge.  , 

If  there  are  other  boilers  in  operation,  and  stop-valves  are  to  be 
opened  to  place  boilers  in  connection  with  others  on  a  steam-pipe 
line,  watch  those  recently  fired  up,  until  pressure  is  up  to  that  of  the 
other  boilers  to  which  they  are  connected;  and,  when  that  pressure  5s 
attained,  open  the  stop-valves  very  slowly  and  carefully. 


BOILER    ACCESSORIES. 


TABLE  OF  PROPERTIES  OF  SATURATED  STEAM. 


Pressure 
in 
pounds 
per  sq.in. 
above 
vacuum. 

Tempera 
ture  in 
degrees 
Fahren- 
heit. 

Total 
heat  in 
heat 
units 
from 
water  at 
32°. 

Heat 
in 
liquid 
from 
32?  in 
units. 

Heat  of 
vaporiza- 
tion, or 
latent 
heat  in 
heat  units. 

Density  or 
weight 
of  cubic  ft. 
in  pounds. 

Volume 
of  one 
pound  in 
cubic 
feet. 

Factor 
of 
equiva- 
lent 
evapora- 
tion 
at  212°. 

Total 
pressure 
above 
vacuum. 

1 

101.99 

1113.1 

70.0 

1043.0 

0.00299 

334.5 

.9661 

1 

2 

126.27 

1120.5 

94.4 

1026.1 

0.00576 

173.6 

.9738 

2 

3 

141.62 

1125.1 

109.8 

1015.3 

0.00844 

118.5 

.9786 

3 

4 

153.09 

1128.6 

121.4 

1007.2 

0.01107 

90.33 

.9822 

4 

5 

162.34 

1131.5 

130.7 

1000.8 

0.01366 

'  73.21 

.9852 

5 

6 

170.14 

1133.8 

138.6 

995.2 

0.01622 

61.65 

.9876 

6 

7 

176.90 

1135.9 

145.4 

990.5 

0.01874 

53.39 

.9897 

7 

8 

182.92 

1137.7 

151.5 

986.2 

0.02125 

47.06 

.9916 

8 

9 

188.33 

1139.4 

156.9 

982.5 

0.02374 

42.12 

.9934 

9 

10 

193.25 

1140.9 

161.9 

979.0 

0.02621 

38.15 

.9949 

10 

14.7 

212 

1146.6 

180.9 

*965.7 

0.03794 

26.36 

1.0000 

14.7 

15 

213.03 

1  146.9 

181.8 

965.1 

0.03826 

26.14 

1.0003 

15 

20 

227.95 

1151.5 

196.9 

954.6 

0.05023 

19.91 

1.0051 

20 

25 

240.04 

1155.1 

209.1 

946.0 

0.06199 

16.13 

1.0099 

25 

30 

250.27 

1158.3 

219.4 

938.9 

0.07360 

13.59 

.0129 

30 

35 

259.19 

1161.0 

228.4 

932.6 

0.08508 

11.75 

.0157 

35 

40 

267.13 

1163.4 

236.4 

927.0 

0.09644 

10.37 

.0182 

40 

45 

274.29 

1165.6 

243.6 

922.0 

0.1077 

9.285 

.0205 

45 

50 

280.85 

1167.6 

250.2 

917.4 

0.1188 

8.418 

1.0225 

50 

55 

286.89 

1169.4 

256.3 

913.1 

0.1299 

7.698 

1.0245 

55 

60 

292.51 

1171.2 

2(il.9 

909.3 

0.1409 

7.097 

1.0263 

60 

65 

297.77 

1172.7 

267.2 

905.5 

0.1519 

6.583 

1.0280 

65 

70 

802.71 

1174.3 

272.2 

902.1 

0.1  628 

6.148 

.0295 

70 

76 

307.38 

1175.7 

276.9 

898.8 

0.1736 

5.760 

.0309 

75 

80 

311.80 

1177.0 

281.4 

895.6 

0.1843 

5.426 

.0323 

80 

85 

316.02 

1178.3 

285.8 

892.5 

0.1951 

5.126 

.0337 

85 

90 

320.04 

1179.6 

290.0 

889.6 

0.2058 

4.859 

1.0350 

90 

95 

323.89 

1180.7 

294.0 

886.7 

0.2165 

4.619 

1.0362 

95 

100 

327.58 

1181.9 

297.9 

384.0 

0.2271 

4.403 

1.0374 

100 

105 

331.13 

1182.9 

301.6 

88  1.3 

0.2378 

4.205 

1.0385 

105 

110 

334.56 

1184.0 

305.2 

878.8 

0.2484 

4.026 

1.0396 

110 

115 

337.86 

1185.0 

308.7 

876.3 

0.2589 

3.862 

.0406 

115 

12D 

341.05 

1186.0 

312.0 

874.0 

0.2695 

3.711 

.0416 

120 

125 

344.13 

1186.9 

315.2 

871.7 

0.2800 

3.571 

.0426 

125 

130 

347.12 

1187.8 

318.4 

869.4 

0.2904 

3.444 

.0435 

130 

140 

352.85 

1189.5 

324.4 

865.1 

0.3113 

3.212 

.0453 

140 

150 

358.  2t> 

1191.2 

330.0 

861.2 

0.3321 

3.011 

.0470 

150 

1GO 

363.40 

1192.8 

335.4 

857.4 

0.3530 

2.833 

.0486 

160 

170 

368.29 

1194.3 

340.5 

853.8 

0.3737 

2.676 

.0502 

170 

180 

372.97 

1195.7 

345.4 

850.3 

0.3945 

2.535 

.0517 

180 

190 

377.44 

1197.1 

350.1 

847.0 

0.4153 

2.408 

.0531 

190 

200 

381.73 

1198.4 

354.6 

843.8 

0.4359 

2.294 

.0545 

200 

225 

391.79 

1201.4 

365.1 

836.3 

0.4876 

2.051 

.0576 

225 

250 

400.99 

1204.2 

374.7 

829.5 

0.5393 

1.854 

.0605 

250 

275 

409.50 

1206.8 

383.6 

823.2 

0.5913 

1.691 

.0632 

275 

300 

417.42 

1209.3 

391.9 

817.4 

0.644  . 

1.553 

.0657 

300 

325 

424.82 

1211.5 

399.6 

811.9 

0.696 

1.437 

.0680 

325 

350 

431.90 

1213.7 

406.9 

806.8 

0.748 

1.337 

.0703 

350 

375 

438.40 

1215.7 

414.2 

801.5 

0.800 

1.250 

.0724 

375 

400 

445.15 

1217.7 

421.4 

796.3 

0.853 

1.172 

1.0745 

400 

•500 

466.57 

1224.2 

444.3 

779.9 

1.065 

.939 

1.0812 

500 

In  this  book  the  use  of  966  in  place  of  965.7  will  be  sufficiently  accurate. 


260 


VERTICAL    TRIPLE    EXPANSION    PUMPING    ENGINE 
ALLIS-CHALMERS    COMPANY 


STEAM  PUMPS, 


Principles  of  Action.  A  pump  is  primarily  a  machine  de- 
signed  for  lifting'liquids,  or  for  conveying  them  to  a  distance  through 
pipes,  or  both.  To  accomplish  these  results  may  be  used  the  prin- 
ciples of  suction,  lifting,  or  forcing  or  any  combination  of  them;  in 
practice  generally  the  first  is  combined  with  one  of  the  other  two. 

Suction,  so-called,  is  really  the  pressure  due  to  the  weight  of 
the  atmosphere  acting  to  force  the  liquid  into  a  space  wherein  a 
partial  vacuum  has  been  created  by  removing  a  part  of  the  matter 
that  filled  it.  The  amount  of  pressure  available  in  any  instance 
for  forcing  in  the  liquid,  depends  upon  the  completeness  with 
which  the  matter  has  been  removed  from  the  space  in  which  suc- 
tion is  acting,  and  on  the  wreight  of  the  atmosphere  at  that  place. 
If  all  matter  could  be  removed  from  the  suction  chamber,  a  perfect 
vacuum  would  be  created  and  the  full  pressure  of  the  atmosphere 
would  be  effective;  a  condition  closely  approaching  this  is  created 
in  the  barrel  of  a  pump  when  no  air  is  present  and  the  plunger  or 
part  of  the  liquid  is  withdrawn. 

If  there  be  any  air  present,  it  will  expand  and  fill  the  vacant 
space,  its  pressure  falling  as  the  volume  increases;  the  pressure 
available  to  force  in  the  liquid  by  suction  will  be  the  difference 
between  that  due  to  the  weight  of  the  atmosphere  and  the  final 
pressure  in  the  suction  chamber.  The  greater  the  amount  of  mat- 
ter removed  from  the  suction  chamber,  the  less  will  be  the  result- 
ing pressure  therein  and  the  greater  the  difference  available  for 
moving  the  liquid. 

The  other  factor,  the  weight  of  the  atmosphere,  varies  with 
its  condition  and  the  altitude  as  shown  by  the  barometer.  The 
following  table  compiled  from  "  Kent's  Mechanical  Engineers' 
Pocket  Book"  and  "  Kystrom's  Mechanics'^  gives  barometer  read- 
ings,  the  pressure  per  square  inch,  and  heights  above  sea  level  cor- 
responding  to  each  other;  the  altitude  being  at  40°  latitude  and 
temperature  GO0  Fahrenheit. 


263 


STEAM  PUMPS 


TABLE  I. 


Barometric  Reading 
in 
Inches  of  Mercury. 

Atmospheric  Pressure 
in  Pounds 
per  Square  Inch. 

Altitude  above 
Sea  Level  in 
Feet. 

30 

14.72 

0 

29.75 

14.60 

232 

29.50 

14.47 

466 

29.25 

14.35 

703 

29.00 

14.23 

941 

28.75 

14.11 

1181 

28.50 

13.98 

1424 

28.25 

13.86 

1668 

28.00 

13.74 

1915 

27.50 

13.50 

2415 

27.00 

13.26 

2924 

26.50 

13.02 

3443 

26.00 

12.77 

3972 

25.50 

12.53 

4511 

25.00 

12.27 

5061 

24.50 

12.03 

5621 

24.00 

11.78 

6194 

23.50 

11.54 

6778 

23.00 

11.30 

7375 

22.50 

11.05 

7985 

22.00 

10.80 

8609 

21.50 

10.56 

9247 

21.00 

10.31 

9900 

20.00 

9.81 

11254 

19.00 

9.32 

12678 

18.00 

8.82 

14179 

17.00 

8.33 

15766 

16.00 

7.84 

17448 

15.00 

7.35 

19240 

14.00 

6.86 

21155 

13.00 

6.37 

23212 

12.00 

5.88 

254a3 

11.00 

5.39 

27848 

STEAM  PUMPS 


As  the  weight  of  a  column  of  water  one  foot  high  and  one 
inch  square  is  0.433  pound,  it  follows  that  the  atmospheric  pressure, 
which  at  sea  level  is  ordinarily  14.72  pounds  per  square  inch,  can 
support  a  column  of  water  as  many  feet  high  as  0.433  is  contained 
in  14.72  or  34.2  feet.  The  height  of  column  which  can  be  sup. 
ported  decreases  as  the  altitude  increases.  At  the  top  of  a  moun- 
tain two  miles  high  it  would  be  only  9.81  -=-  0.433  =  22.7  feet. 

This  is  the  height  which  could  be  barely  supported  if  the 
vacuum  were  perfect.  In  practice  the  height  to  which  water  can 
be  lifted  is  much  less,  because  it  is  impossible  to  obtain  a  perfect 
vacuum  on  account  of  leakage  of  valves  and  joints,  and  the  atmos- 
pheric pressure  must  overcome  friction  in  pipes  and  passages,  so 
that  the  possible  lift  is  reduced  to  not  over  25  feet  at  sea  level  and 
this  only  for  slow  working.  It  is  better  to  attempt  only  20  feet  or 
even  less  if  the  pump  is  to  work  rapidly.  If,  however,  a  high 
suction  lift  is  imperative,  it  may  be  obtained  by  admitting  air  with 
the  watt>r  in  suitable  proportions  to  form  a  heavy  spray  so  that 
the  weight  per  cubic  foot  of  the  mixture  is  considerably  reduced. 
In  this  way  a  lift  of  as  much  as  100  feet  may  be  possible,  but  of 
course,  at  the  expense  of  the  weight  of  water  pumped  pei  stroke, 
so  that  either  the  pump  must  be  run  at  a  higher  speed  or  a  larger 
pump  must  be  used.  The  air  should  be  admitted  to  the  suction 
pipe  through  several  small  openings  a  little  above  the  level  of  the 
water  in  the  supply  reservoir.  The  suction  must  be  primed  each 
time  the  pump  is  started. 

Probably  the  earliest  example  of  a  practical  steam  pump  was 
that  built  at  Raglan  Castle  by  the  Marquis  of  "Worcester  in  1630. 
This  employed  both  suction  and  pressure,  two  vessels  making  the 
How  continuous.  Steam  was  admitted  from  a  boiler  through  valve 
B',  Fig.  1,  to  the  chamber  A',  and  the  pressure  forced  the  water 
upwards  through  the  valve  F'and  pipe  E;  the  valve  C' preventing 
its  return  to  the  reservoir.  Meantime  the  chamber  A  was  shut  off 
from  the  boiler,  and  the  cold  water,  condensing  the  steam,  caused 
a  partial  vacuum  so  that  water  was  forced  up  through  valve  C-and 
pipe  D  into  the  chamber  A.  When  A'  was  emptied  and  A  filled^ 
the  steam  valves  were  reversed  and  A'  became  filled  while  A  was 
being  emptied. 

Practically  all  pumps,  except  those  to  which  the  liquid  comes 


265 


STEAM  PUMPS 


under  pressure,  use  the  suction  principle  for  filling  their  cylinders. 
The  suction  lift  is,  however,  usually  but  a  few  feet  except  where 
deep  mines  are  drained,  and  in  the  case  of  air  pumps  for  condens- 
ers in  which  the  suction  is  always  kept  at  the  highest  possible 
value.  In  order  to  improve  the  suction  action,  valves  and  supply 


Fig.  1. 


Fig.  2. 


pipes  must  be  kept  with  all  seatings  and  joints  absolutely  tight. 
Lifting.  The  lifting  pump  is  simply  a  bucket  13,  Fig.  2, 
working  in  a  vertical  barrel  A  and  so  arranged  that  the  water  is 
caught  above  the  bucket  and  raised  on  the  upward  stroke  to  the 
top  of  the  barrel  or  to  a  point  where  an  overflow  is  provided. 
Usually  the  bucket  is  filled  on  the  down  stroke  by  means  of  a  valve 


WORTH1NGTON  STEAM   PUMP,  SHOWING   ARRANGEMENT   OF   WORKING   PARTS. 


STEAM  PUMPS 


0  in  the  bottom,  and  if  the  lift  is  for  any  considerable  distance,  it 
is  necessary  to  put  a  foot  valve  E  at  the  bottom  of  the  inlet  pipe  to 
prevent  the  liquid  from  sinking  in  the  barrel  when  the  bucket  de- 
scends. By  this  means  suction  also  is  introduced,  since  the  space 
D  above  the  foot  valve  is  filled  from  the  reservoir  by  suctiot  dur. 
ing  the  up  stroke  of  the  bucket.  The  pump  may  then  be  placed 
at  any  distance  above  the  reservoir  within  the  limit  already  stated, 
and  at  any  distance  horizontally;  but  it  should  be  remembered  that 
the  speed  of  working 
and  height  of -lift  must 
be  decreased  if  the  hori- 
zontal distance  is  ma- 
terially increased,  and 
that  it  is  always  better 
to  make  the  suction 
pipe  as  short  as  pos- 
sible. 

Forcing.  The  suc- 
tion effect  is  used  in 
all  pumps,  at  least  to 
fill  the  barrel,  but  the 
lifting  principle  is  un- 
common except  where 
the  discharge  is  to  be 
directed  from  a  spout 
at  the  top  or  in  the  side 
of  the  barrel,  as  in  mine 
drainage  and  house 
pumps.  If  it  is  neces- 
sary to  raise  the  liquid 
to  a  point  above  the  pump  level,  either  a  piston  or  a  plunger  work- 
ing in  a  closed  chamber  is  used  to  force  the  liquid  through  dis- 
charge valves,  against  whatever  pressure  may  be  necessary,  into 
the  delivery  pipe;  return  currents  being  prevented  by  the  closing 
of  the  discharge  valves. 

As  seen  in  Fig.  3,  the  plunger  P  on  the  outward  stroke  draws 
water  from  the  reservoir  through  pipe  A  and  inlet  valves  E  into 
the  barrel  B.  On  the  inward  stroke,  the  valve  E  will  close  and, 


Fig.  3. 


267 


8  STEAM  PUMPS 


since  liquids  are  practically  incompressible,  the  discharge  valves 
D  will  open  allowing  the  water  to  pass  into  the  discharge  chamber 
and  out  the  pipe  C.  Fig.  3  represents  a  single-acting  plunger 
pump,  but  the  action  is  the  same  for  a  piston  or  for  a  double-acting 
pump  except  that  there  are  two  sets  of  valves.  Although  the  force 
is  exerted  on  the  mass  of  liquid  in  a  direction  lengthwise  of  the 
barrel,  yet,  since  pressure  is  transmitted  equally  in  all  directions, 
the  valves  will  open  promptly  if  located  in  any  position  with  respect 
to  the  barrel. 

The  pressure  against  which,  the  pump  must  act  in  forcing  de- 
pends on  the  weight  of  the  valves,  the  spring  pressure,  if  any,  used 
to  close  them  quickly  and  the  height  to  which  the  liquid  is  to  be 
raised,  or  as  it  is  technically  termed,  the  "  head,"  against  which  the 
pump  is  to  work.  For  water,  the  pressure  per  square  inch  in- 
creases  one  pound  for  every  2.32  feet,  or  as  previously  stated  one 
foot  of  head  produces  0.433  pound  pressure  per  square  inch.  There 
is  no  theoretical  limit  to  the  height  to  which  a  liquid  may  be  raised 
by  forcing,  but  the  speed  of  starting  and  stopping  the  column  of 
water,  that  is,  the  number  of  strokes  per  minute,  must  be  decreased 
as  the  delivery  pipe  becomes  longer,  if  water-hammer  is  to  be  avoid- 
ed; this  is  true  whether  the  length  be  horizontal  or  vertical.  This 
hammer  effect  is  due  to  the  force  necessary  to  overcome  the  inertia 
of  the  column  of  liquid  and  start  or  stop  its  motion.  If  not  prop- 
erly taken  into  account,  either  by  using  slow  speeds  or  providing 
adequate  air  chambers  to  take  up  the  shock,  it  will  always  produce 
destructive  results.  Wear  on  the  outlet  valves  also  limits  the 
height  to  which  water  may  be  forced,  as  this  wear  increases  with 
the  head  and  makes  it  difficult  to 'keep  the  valves  tight. 

Usually  no  special  precautions  are  required  up  to  pressures  of 
500  pounds  per  square  inch;  above  this,  care  must  be  exercised  up 
to  the  limit  of  2,000  pounds,  which  is  as  high  as  will  be  required 
for  lifts  or  presses  except  in  special  cases.  Anything  above  this 
requires  the  greatest  precautions,  not  only  as  to  strength  of  parts, 
form  of  valves  and  packing  of  joints,  but  even  with  respect  to 
quality  of  castings.  "Water  will  sometimes  leak  through  what  ap- 
pears to  be  solid  metal. 

The  pressure  produced  by  water-hammer  is  taken  advantage 
of  in  one  special  form  of  pump,  the  hydraulic  ram.  in  which  the 


268 


STEAM    PUMPS 


TABLE   II. 


Head 
in 
feet. 

I                  1 

Pressure                 Head                 Pressure 
pounds  per                in                 pounds  per 
square  inch.              feet.         j      square  inch. 

Head 
in. 
feet. 

Pressure 
pounds  per 
square  inch. 

1 

.43                46 

19.92 

91 

39  .  42 

2 

.  S6                47 

20.35 

92         i     39.85 

3 

1.30                 4S 

20  .  79 

93              40  .  28 

4 

1  .  73                 49 

21  .22 

94              40.72 

5 

2.16 

50 

21.65 

95 

41.15 

6 

2.59 

51 

22.09 

96 

41.58 

7 

3.03 

52 

22  .  52 

97 

42.01 

8 

3  .  46 

53 

22  .  95 

98 

42  .45 

9 

3.89 

54 

23.39 

99 

42  .  88 

10 

4.33 

55 

23.82 

100 

43.31 

11 

4.76 

56 

24  .  26 

101 

43  .  75 

12 

5.20 

57 

24  .  69 

102 

44.18 

13 

5  .  63 

58 

25.12 

103             44.61 

14 

6.06 

59 

25.55 

104             45.05 

15 

6  .  49 

60 

25.99 

105             45.48 

16 

6.92 

61 

26.42 

106             45.91 

17 

7.36 

62 

26.85 

107             46.34 

18 

7.79 

63 

27  .  29 

108         :     46  .  78 

19 

8  .  22 

64 

27  .  72 

109 

47.21 

-20 

8.66 

65 

28  .  15 

110 

47.64 

21 

9.09 

66 

28  .  58 

111 

48.08 

22 

9.53 

67 

29.02 

112 

48.51 

23 

9.96 

86 

29.45 

113 

48.94 

24 

10.39 

69 

29.88 

114 

49.38 

25 

10.82 

70 

30  .  32 

115 

49.81 

26 

1  2  .  26 

71 

30.75 

116 

50  .,24 

27 

1  1  .  69 

72 

31.18 

117 

50.68 

28 

12.12 

73 

31  .62 

118 

51.11 

29 

12.55 

74 

32.05 

119 

51.54 

30 

1  2  .  99 

75 

32.48 

120 

51  .  98 

31 

13.42 

76 

32.92 

121 

52.41 

32 

13.86 

77 

33.35 

122 

52.84 

33 

14.29 

78 

33.78 

123 

53.28 

34 

14.72 

79 

34  .  21 

124         ;     ,53.71 

35 

15.16 

SO 

34.65 

125         >    .54.15 

36 

15.59 

81 

35.08 

126         !     54.58 

37 

16.02 

82 

35.52 

127 

,55.01 

38 

16.45 

83 

35.95 

128 

.55.44 

39 

16.89 

84 

36.39 

129 

55.88 

40 

17.32 

85 

36.82 

130 

56.31 

41 

17.75 

86               37  .  25 

131 

56.74 

42 

18.19 

87               37.68 

132 

57.18 

43 

18.62 

88               38.12 

133 

57.61 

44 

19.05 

89       :        38.55 

'    134 

58.04 

45 

19.49 

90               38  .  98 

135         I    58.18 

269 


10 


STEAM  PUMPS 


force  produced  by  the  inertia  of  a  large  column  of  water  suddenly 
checked  is  utilized  to  raise  a  small  column  against  a  high  pressure. 
The  working  of  the  apparatus  is  seen  from  Fig.  4.  Water  flowing 
from  pipe  F  into  the  chamber  A  will  escape  through  valve  Y 
(closed  in  the  figure)  to  discharge  pipe  D;  but,  as  the  velocity  of 
flow  increases,  valve  V  will  be  lifted  and  closed  checking  the  flow 
of  water.  The  force  thus  developed  will  open  valve  V  against 
the  pressure  of  the  spring  and  the  head  of  water  in  the  small  pipe 
E,  and  some  water  will 
be  forced  into  cham- 
ber B  and  up  pipe  E 
or  into  the  air  cham- 
ber C  compressing  the 
air.  Water  will  pass 
into  B  until  the  force 
due  to  water  hammer 
is  so  decreased  that 
valve  V  closes  and 
valve  V  opens  once 
more,  when  water  will 
ao-ain  overflow  and  the 

O 

process  be  repeated. 
The  head  against 
which  the  ram  will 
work  may  be  almost 
any  amount,  but  the  ratio  of  water  raised  to  that  wasted  at  the  over- 
flow will  decrease  as  the  head  on  valve  V  increases.  In  any  case, 
the  -ratio  will  be  small  and  the  ram  wasteful,  so  that  its  use  is 
advisable  only  where  the  supply  of  water  is  almost  unlimited,  other 
power  is  difficult  to  procure,  or  the  amount  to  be  raised  is  very 
small.  Table  III  gives  the  relation  of  efficiencies  and  ratio  of 
lifting  to  forcing  heads,  which  according  to  I).  K.  Clark,  may 
fairly  be  expected  with  a  ram  of  good  design.  . 


Fig.  4. 


TABLE  III. 


G       8 
01     52 


Ratio  of  lift  to  fall     4 
Efficiency  per  cent    72 

'The  ram  should  be  arranged  with  a  drive  pipe  whose  length  is 


10 
44 


12 

37 


14 
81 


10     18 

25    iy 


20 
14 


870 


STEAM  PUMPS  11 


at  least  five  times  the  fall,  in  order  to  give  a  long  column  of  inov. 
ing  water  and  increase  the  water-hammer.  The  diameter  of  drive 
pipe  is  usually  twice  that  of  the  lift  pipe. 

KINDS  OF  PUflPS. 

In  classifying  pumps,  the  division  may  be  made  according  to 
any  one  of  several  methods:  As  to  the  principles  of  action,  the  de- 
tails of  construction,  the  means  of  driving,  or  the  purposes  for 
which  they  are  used.  With  respect  to  principle  of  action  the  classes 
may  be: 

1.  Lifting, 

2.  Forcing, 

3.  Combinations. 

With  regard  to  the  details  of  construction* 

1.  Jet, 

2.  Rotary, 

3.  Centrifugal, 

4.  Reciprocating. 

With  regard  to  uses,  the  division  is  difficult,  since  the  sam& 
pump  is  frequently  used  in  different  places  for  different  purposes. 
Such  classes  as  tank  pumps,  boiler-feed  pumps,  air  pumps  and 
mine  pumps  are  fairly  definite,  but  the  details  vary  so  much  with 
different  makers  that  it  is  impossible  to  draw  sharp  distinctions. 

From  the  discussion  of  the  principles  of  action  we  know  that 
practically  all  power  pumps  are  of  the  third  class,  that  is,  work  by 
a  combined  lifting  action  due  to  suction  and  forcing.  But  the 
second  classification  is  yet  to  be  considered. 

The  Jet  Pump.  The  first  variety,  the  jet  pump,  is  perhaps 
best  known  in  the  form  of  the  injector,  but  the  principle  is  worthy 
of  a  much  wider  application  than  it  now  has.  In  the  form  of  a 
steam  or  water  ejector  it  may  be  used  for  lifting  water  by  suction 
and  raising  it  to  a  considerable  height,  while  its  simplicity  and 
ease  of  application  give  it  a  large  field  of  usefulness.  A  convenient 
form  for  an  ejector  is  shown  in  Fig.  5.  The  propelling  jet  may 
be  either  steam  or  water  under  pressure  entering  through  the  valve 
A  and  flowing  from  nozzle  D  which  should  be  made  with  a  de- 
creasing taper  like  a  hose  nozzle.  If  steam  is  used,  it  will  be 
necessary  to  provide  a  small  injection  pipe  with  valve  for  supply, 
ing  water  to  condense  the  jet  and  create  a  vacuum  at  the  start, 
otherwise  the  steam  will  blow  through  the  apparatus  ,-ind  will  not 


271 


12  STEAM  PUMPS 


lift  the  water  in  the  suction  pipe.  In  this  case,  the  heat  energy  of 
the  steam  will  be  converted  into  velocity,  and  will  be  available  for 
drawing  and  forcing  the  water  so  that  it  can  be  raised  to  a  consid- 
erable height.  The  efficiency  of  a  well-designed  steam  ejector 
should  bo  nearly  equal  to  that  of  an  injector  and  will,  like  that, 
depend  on  the  temperature  of  the  water  and  the  height  of  the  suc- 
tion and  lift. 

In  pumping  into  a  boiler,  the  efficiency  of  an  injector  is  nearly 
100  per  cent  because  nearly  all  the  heat  energy  which  is  lost  iu 
friction  goes  to  heat  up  the  feed  water  and  is  therefore  utilized; 


,  SUCTION 
Fig.  5. 

but  for  other  purposes,  the  injector  or  ejector  is  wasteful  of  heat 
and  cannot  bo  considered  economical.  Its  convenience,  however, 
is  a  strong  point  in  its  favor,  and  where  the  amount  of  water  to  be 
lifted  is  not  large,  or  if  it  is  to  be  used  only  occasionally,  it  will 
often  pay  to  use  it  rather  than  to  install  a  more  elaborate  and 
costly  pump. 

When  water  under  pressure  is  used  as  driving  power,  it  is  not 
necessary  to  have  the  inlet  at  B.  The  flow  of  the  water  from  the 
nozzle  will  carry  along  the  air  and  create  a  vacuum  at  D  which 
will  draw  the  water  up  the  pipe  C.  There  is  no  heat  energy  avail- 
able as  in  the  case  of  steam,  so  that  the  water  can  furnish  only  such 
an  amount  of  power  as  is  due  to  its  weight  and  the  velocity  with 


272 


STEAM  POMPS 


13 


DISCHARGE 


which  it  leaves  the  ejector  nozzle;  and,  as  the  efficiency  is  low,  not 
over  one  fourth  of  the  energy  furnished  to  the  ejector  at  A  will  be 
available  to  move  water  at  E.  For  a  water  injector  it  is  well  to 
proportion  the  pipes  so  that  the  head  on  A  times  the  area  of  D 
equals  twice  the  suction  and  lifting  heads  combined  multiplied  by 
the  area  of  C;  and  to  make  the  area  of  E  equal  to  the  area  of  D 
plus  the  area  of  C,  if  the  apparatus  is  to  be  used  as  a  water  ejector. 
For  steam,  a  ^-inch  pipe  at  A  for  a 
2-inch  at  C  and  a  2^-inch  at  E  has 
been  found  to  work  well  when  the 
head  on  E  was  small,  and  if  the  water 
is  under  city  pressure  a  |--inch  pipe 
atB. 

It  is  well  to  remember  that  the  en- 
ergy  of  a  jet  of  either  steam  or  water 
depends  more  on  the  velocity  than  on 
the  weight  flowing,  since  the  energy 

available  per  second  equals-^ — where 

W  is  the  weight  flowing  per  second, 

v  is  the  velocity  in  feet  per  second  and 

g  is  the  acceleration  due  to  gravity;  therefore,  for  good  efficiency, 

it  is  best  to  use  high  pressure  whenever  possible. 

Rotary  Pumps.  These  have  been  but  little  used  because,  as 
usually  designed,  their  efficiency  has  been  low.  They  are,  how- 
ever,  useful  in  many  cases  and  are  well  adapted  for  moving  large 
volumes  of  liquid  at  low  pressures.  This  pump  moves  the  liquid 
by  catching  it  between  the  lobes  of  the  revolving  propellers  and 
the  casing  of  the  pump  and  sweeping  it  around  from  the  suction 
pipe  to  the  discharge  ;  its  return  being  prevented  by  the  obstacle 
of  the  lobes  and  cylinders  in  the  center.  All  are  made  on  the  same 
principle,  the  difference  being  in  the  design  of  the  lobes  and 
cylinders. 

These  are  of  many  forms,  but  two  will  be  sufficient  to  illustrate 
the  principles.  Fig.  6  is  the  Berrenberg;  here  the  lobes  are 
made  by  two  pieces  of  tube  fastened  opposite  each  other.  The 
tubes  extend  from  the  semi -cylindrical  openings  and  make  a  joint 
with  the  other  lobe  by  fitting  in  as  shown.  The  axles  are  geared 


273 


TUMI'S 


together  outside  the  casing  and  are  supported  by  bearings 
inside  and  outside,  which  are  tapered  to  allow  taking  up 
wear  and  keeping  the  shafts  true.  The  curves  in  Fig.  7  show 
the  results  from  a  series  of  tests  made  on  a  2-inch  pump  by  Mr. 
R.  A.  Hale  and  recorded  in  Barr's  "  Pumping  Machinery."  These 
show  that  the  efficiency  of  the  pump  increases  with  the  pressure 
against  which  it  is  working  up  to  a  certain  point,  and  then  falls 
off,  while  comparison  of  the  curves  at  different  speeds  shows  that 

RELATION    OF   EFFICIENCY   TO   PRESSURE 
FOR    ROTARY    PUMPS. 


£60 

Ul 
0 

BE 

HI  40 
Q. 


O  20  40  60  80  100 

POUNDS    PRESSURE   PER  SQUARE    INCH. 

Fig.  7. 

the  efficiency  becomes  less  as  the  speed  increases.  This  is  apparent 
because  the  loss  from  friction  is  not  doubled  by  doubling  the  head, 
while  the  amount  of  water  will  be  the  same  per  revolution,  no 
matter  what  the  pressure  may  be.  The  exception  to  this  is  due  to  slip 
which  increases  as  the  pressure  becomes  greater.  Hence  the  useful 
work  will  increaie  up  to  that  point  where  the  loss  due  to  leakage 
and  friction  more  than  balances  the  increase  of  work  due  to  the 
increased  head.  The  same  reasoning  applies  to  the  speed,  except 
that  in  this  case  the  friction  work  will  increase  in  proportion  to  the 
speed,  BO  that  the  gain  from  the  added  work  due  to  the  increase  of 
speed  is  not  as  great  aa  from  increase  of  head. 

Another  style  of  rotary  pump  is  shown  in  Fig.  8  in  which  the 
two  pistons  are  so  designed  that  their  bounding  surfaces  are  always 


374 


STEAM  PUMPS  15 


in  contact,  thus  forming  the  joint.  In  this  type  it  is  important 
that  the  surfaces  be  of  the  correct  shape,  otherwise  a  pocket  will 
be  formed  in  which  water  will  be  caught.  This  water  will  be  com. 
pressed  as  the  volume  of  the  pocket  becomes  smaller.  As  water  is 
practically  incompressible,  it  must  either  leak  past  the  joint  or 
burst  the  pump.  In  order  to  prevent  this,  a  port  is  sometimes 
cut  in  the  casing  to  allow  the  water  to  bypass  and  relieve  the  pres- 
sure.  If,  however,  the  outline  of  the  lobes  is  made  of  the  right 
shape,  there  will  be  no  compression  and  the  ports  will  not  be  nee- 


Fig.  8. 

essary.  It  has  been  demonstrated  that  the  curves  to  use  for  the 
outline  of  the  lobes  are  the  cycloids,  as  they  can  form  the  whole 
outline  and  will  make  a  smooth  surface  which  will  not  create 
pockets  at  any  part  of  the  revolution.  The  involute  curve  has 
sometimes  been  used,  but  it  is  not  good  as  it  does  not  return  on 
itself,  and  must  therefore  be  cut  off  by  the  arc  of  a  circle  on  the 
end  of  the  lobe,  leaving  corners  which  form  compression  pockets. 
"With  respect  to  the  effect  of  the  speed  on  the  volume  of  water 
pumped,  the  experiments  above  noted  showed  that,  within  the 
stated  limits,  the  volume  varies  nearly  as  the  speed,  and  that  at 
the  same  speed,  the  volume  is  a  little  less  at  high  pressure  than 
at  low,  but  does  not  fall  off  rapidly  as  the  pressure  increases.  The 
data,  however,  is  not  complete  enough  to  be  conclusive. 


275 


STEAM  PUMPS 


The  rotary  pump  is  often  used  for  fire  purposes,  and  where 
portability  is  of  more  importance  than  efficiency,  or  if  first  cost  is 

a  great  consideration.  It  can 
be  run  at  high  speed,  and  has 
a  large  capacity  for  the  space 
occupied,  but  it  is  not  suitable 
for  large  or  permanent  work 
except  at  very  low  heads. 

Centrifugal  Pumps.  These 
operate  by  the  familiar  force 
which  throws  the  mud  from 
the  carriage  wheel  and  the 
wrater  from  the  lawn  sprinkler. 
A  wheel  W  (Fig.  9)  with 
curved  blades  revolves  in  a 
casing  C  and,  when  the  cas- 
ing is  filled  with  water, 
throws  it  to  the  outside  thus 
creating  a  suction  at  the  cen- 
ter and  drawing  up  water 
The  velocity  and  whirling  motion 


Fig.  9. 


through  the  suction  pipe  S. 
given  to  the  water  send  it  to  the  outside  of  the  casing  and  out 
through  a  delivery  pipe  P.  As  seen  in  Fig.  9,  the  casing  increases 
in  size  up  to  the  outlet  P,  as  the  volume  of  the  water  to  be 
carried  will  increase  in  that  way.  The  blades  are  given  a  backward 
inclination  at  the  wheel  center  so  that  water  may  enter  without 
shock,  and  the  angle  which  the  blades  make  \vith  the  radius  is 
increased  towards  the  outer  end  so  that  the  water  gradually  attains 
some  rotary  velocity  and  great  radial  velocity  due  to  the  wedging 
action  as  it  passes  outwards;  on  leaving  the  blades  it  has  high 
speed.  If  the  blades  are  radial  at  the  outer  end,  the  discharge 
will  be  greater  for  a  given  speed,  but  it  will  not  be  possible  to 
reduce  the  speed  much  without  stopping  the  action  altogether;  also 
the  efficiency  will  be  less. 

liankine  states  that  the  curve  of  the  blade  should  be  an  involute 
of  a  circle,  that  is,  a  curve  drawn  by  a  point  in  a  string  as  it  is 
unrolled  from  the  circle  as  shown  in  Fig.  10.  The  method  of  draw- 
ing the  involute  is  as  follows:  Let  BC  be  the  inner  bounding  circle 


276 


STEAM  PUMl'S 


17 


of  the  blades  and  B  the  point  at  which  a  vane  is  to  start.     Draw 
a  radius  of  the  circle  through  B  and  through  the  same  point  at  an 
angle  of  40  degrees  with  the  tangent,  another  straight  line  BE. 
Draw  a  concentric  circle  tangent  to  BF,  which  is  perpendicular 
to  BE.     If  B  were  a  point  in  a  string,  and  this  were  unrolled 
from  the  circle,  the  point  B  would  trace  an  involute  BGH.     For 
the  first  form  of  curve  mentioned,  this  would  be  continued  to  the 
outer  bounding  circle  where  it  should  make  an  angle  of  about  15 
degrees  with  the  tangent,  as  LHM.     For  the  Rankine  blade,  the 
reverse  curve  UK  A  should  be  drawn,  usually  the  arc  of  a  circle 
radial  at  the  point  H.     In  order  to  work  without  shock,  the  angle 
of  the  blade  with  the  tangent  at  the  inside  end  B  should  be  such 
that  its  tangent  equals  the  radial  velocity  of  the  water  divided  by 
the   circumferential    velocity 
of  that  point  on  the  wheel;  it 
is   often    made    40    degrees, 
which   is  found   to  be  satis- 
factory for  the  average  case. 
The    angle    at    the    outside 
should  be  15  degrees  if  there 
is  no  diffusing  chamber,  or  if 
the  discharge  pipe  is  not  of 
increasing  diameter,  in  order 
to  gradually  lessen  the  veloc- 
ity of  the  water  after  it  leaves 
the  wheel.     But  this  will  ne- 
cessitate a  high  rotary  veloc- 
ity of  the  blades,  and  it  is 
sometimes  better  to  use  a  diffusing  chamber  (or  an  increasing  dis- 
charge pipe),  and  make  the  blades  of  the  Rankine  form,  running 
the  wheel  at  a  lower  speed  unless  the  conditions  make  it  necessary 
to  be  able  to  run  at  a  given  medium  speed  for  a  partial  discharge. 
The  casing  should  be  shaped  to  give  the  water  a  gradually  increas- 
ing velocity  from  the  time  that  it  enters  the  suction  pipe  until 
it  reaches  the   circumference  of   the  fan,  and  then  a  decreasing 
velocity  until  it  leaves  the  discharge  pipe.     The  spiral  casing  is 
often  recommended  because  the  centrifugal  force  given   by   the 
rotary  motion   is   radial,  not  tangential,  and  the  water  must  be 


Fig.  10 


277 


18 


STEAM  PUMPS 


given  time  to  change  its  direction  or  it  will  spend  much  of  its 
energy  in  eddies  and  useless  work. 

Three  styles  of  blades  are  shown  in  Figs.  11,  12  and  13.     Fig. 
11  is  the  form  used  for  small  sizes  and  for  thick  liquids;  Fig.  12 


Fig.  11. 


Fig.  12. 


is  a  hollow-arm  type  used   in  large  pumps;  it  has  the  advantage 
that  the  water  is  thrown  outward  without  any  churning  motion, 
and  that  there  are  no  dead  spaces.     Fig.  13  is  the  style  used  for 
dredges  and  has  the  advantage  that  the  sand  is 
kept  from  grinding  between  the  blades  and  the 
casing  yet  large  openings  are  free  for  the  passage 
of  sand  and  mud. 

It  is  possible  to  raise  water  to  any  height  up 
to  100  feet  by  increasing  the  speed  of  the  pump, 
but  it  has  been  shown  by  experiment  that  this 
form  is  not  suitable  for  lifts  of  over  25  feet,  al- 
though up  to  35  feet  the  efficiency  is  fairly  good. 
As  it  is  at  these  low  lifts  that  the  reciprocating 
pump  is  least  efficient,  this  is  clearly  the  field 
of  the  centrifugal  pump. 

The  speed  is  increased  as  the  height  or  the 
lift  increases,  but  not  in  exact  proportion,  be- 
cause the  increase  of  speed  for  an  increase  of  10  feet  in  lift  is 
greater  at  low  than  at  high  heads.  Fig.  14  shows  the  relation 
between  head  and  speed  in  two  pumps  of  the  same  make,  the  No.  2 
having  a  capacity  of  100  gallons  per  minute  at  the  speeds  given 


Fig.  13. 


278 


STEAM  PUMPS 


19 


and  the  No.  0  a  capacity  of  1,200  gallons.  The  -point  at  which  the 
curves  cut  the  axis  of  speed  shows  that  the  No.  2  pump  will  fail 
to  work  at  a  speed  below  250  r.  p.  m.  and  the  No.  G  below  125 
r.  p.  m.  -The  pump  may  be  set  in  either  a  vertical  or  a  horizontal 
position  and  may  have  the  suction  on  one  side  or  both.  However, 
it  is  better  on  both  so  that  the  forces  due  to  lifting  the  water  in 
the  suction  pipe  are  balanced  and  no  end  thrust  produced.  It  ia 
necessary  to  have  some  means  of  filling  the  pump  casing  with 


2500 


2000 


a:     1500 

Ul 

Q. 
(I) 

Z. 

°    1000 
0 


500 


<>No.  2 


o  No.  6 


20 


4O  60 

HEAD  IN  FEET. 

Fig.  14. 


,80 


100 


water,  that  is,  "  priming  "  it,  as  the  suction  will  not  start  until  the 
pump  is  BO  primed.  If  water  under  pressure  is  not  available,  it  is 
necessary  to  install  a  steam  injector  to  fill  the  casing,  or  provide  a 
foot  valve  which  will  be  tight  enough  to  hold  the  water  in  the  suc- 
tion pipe  at  all  times. 

Makers  recommend  that  a  flap  valve  be  installed  at  the  top 
end  of  the  discharge  pipe  also,  to  assist  this  action.  Fig.  15  shows 
an  arrangement  which  is  satisfactory  and  also  gives  aii  idea  of  the 
shape  and  relative  proportions  of  a  standard  centrifugal  pump. 

Lifting  Pumps.     The  only  pumps  which  work  entirely  by 


STEAM  PUMPS 


STEAM  INLET 


lifting  are  the  old-fashioned  chain  devices  in  which  a  series  of  discs 

O 

mounted  on  a  chain  are  drawn,  by  a  sprocket  wheel,  up  through  a 
tube  bringing  the  water  with  them.  In  this  form  the  motion  is 
always  in  one  direction,  and  there  is  a  purely  lifting  action.  But 
it  is  common  to  speak  of  the  pump  which  delivers  its  stream  by 
lifting,  as  a  lifting  pump  even  though  it  is  filled  by  the  action  of 
suction.  These  are  used  largely  in  mines  and  for  domestic  pur- 
poses.  The  principle  has  been  shown  in  Fig.  2.  The  disadvantage 
of  this  style  is  that  the  pump  bucket  must  be  not  over  20  feet 
above  the  water  and  the  rest  of  the  lift  must  be  made  by  the  rise 
of  the  bucket,  necessitating  either  a  long  rod,  or  pumping  in  relay. 

The  greatest  use  of  this  class 

O 

was  in  the  Cornish  mines  in 
the  time  of  Watt  when  the  en- 
gines were  placed  at  ground 
level,  and  the  rods  made  of  a 
length  sufficient  to  reach  to 

CD 

within  20  feet  of  the  bottom 
of  the  shaft.  In  some  cases 
these  pump  rods  were  as  much 
as  480  feet  long,  and  the  de- 
sign of  the  great  pieces  was 
a  difficult  problem.  The  walk- 
ing-beam engine  was  used 
largely  to  drive  the  pumps, 
and  the  whole  machine  was  a 
huge  and  wasteful  affair. 

At   the  present   time,  the 
long  pump  rod  is  used  to  some 


DISCHARGE 


FOOT  VALVE 
Fig.  15. 


extent,  but  it  is  driven  by  a  vertical  cylinder  set  over  the  top  of 
the  mine  shaft. 

The  size  of  the  pump  cylinder  depends  upon  the  volume  of 
water  to  be  raised  and  the  speed  of  the  pump.  When  heavy  masses 
are  to  be  moved,  as  is  the  case  when  long  rods  are  used,  the  speed 
must,  of  course,  be  slow.  For  the  great  engines  of  Watt's  time  it 
was  about  15  strokes  per  minute,  and  in  modern  pumps  it  is  25  to 
35  strokes  per  minute.  The  cylinder  must  be  made  of  such  size 
that  at  this  speed  it  will  lift  the  required  amount  of  water. 


STEAM  POMPS  21 


For  example,  if  it  is  desired  to  raise  100  gallons  per  minnte, 
and  the  pump  is  to  run  at  30  strokes,  the  volume  to  be  raised  is 
100x231  =  23,100  cubic  inches,  and  the  volume  per  stroke  is 
23,100  -4-  30  =  770  cubic  inches.  A  usual  value  for  the  stroke  of 
pumps  of  this  size  is  16  inches  which  (if  there  were  no  allowance 
for  leakage)  would  make  the  area  of  the  cylinder  770  -f-  16  =  48.13 
square  inches.  The  allowance  for  leakage  or  slip  should  be,  for  a 
pump  of  this  size  and  speed,  about  3  per  cent.  This  would,  of  course, 
increase  with  high  speed  and  decrease  with  large  size.  Allowing 
3  per  cent  slip,  the  area  should  be  48.13x1.03=49.58  square 
inches  which  is  that  for  a  circle  of  about  7||  inches  diameter,  so 
that  8  inches  would  be  used  and  the  area  would  then  be  50.26 
square  inches. 

To  find  the  force  needed  to  lift  this  bucket,  it  is  necessary  to 
know  the  height  to  which  the  water  is  to  be  raised.  Suppose  this  to 
be  200  feet;  then  the  pressure  per  square  inch  will  be  200  X  .433  = 
86.60  pounds  and  the  force  needed,  86.60  X50.26=4,352+pounds 
To  this  must  be  added  the  weight  of  the  bucket  and  rod  as  both- 
must  be  lifted  at  each  stroke  by  the  driving  head  at  the  top  of  the 
shaft.  The  rods  are  usually  made  of  wood  with  the  sections 
fastened  together  by  iron  couplings.  The  proper  size  for  the 
above  pump  is  4  inches  diameter,  which  for  a  rod  200  feet  long 

7TX  42 

would  weigh,  at  45  pounds  per  cubic  foot,  45  X  X  200  =785 

4  X  144 

pounds  (about),  and  the  bucket  and  fastenings  will  easily  make 
this  1,000  pounds;  the  whole  weight  to  be  lifted  will  then  be  5,352 
pounds,  which,  at  30  strokes  per  minute,  will  call  for  the  expendi- 
ture of 


This  would  be  the  power  necessary  to  run  the  pump  aside 
from  the  friction  of  the  machinery. 

Although,  at  the  present  time,  high  lifts  are  largely  made  by 
using  a  forcing  pump  at  the  bottom  of  the  shaft,  this  was  not 
known  at  the  time  of  the  introduction  of  the  pumping  engine  in 
the  Cornish  mines,  and  when  it  was  necessary  to  raise  water  from 
a  depth  greater  than  could  well  be  handled  in  one  lift,  it  was 
accomplished  by  using  pumps  in  relays.  One  engine  would  be 


281 


22 


STEAM  PUMPS 


installed  at  a  depth  of  some  240  feet  from  the  bottom  of  the 
mine,  with  its  pump  cylinder  within  20  feet  of  the  bottom, 
and  would  raise  the  water  into  a  reservoir  from  which  it  would  be 
taken  by  another  pump  and  BO  on.  Instances  are  recorded  in  which 
pumps  raised  4,014,800  gallons  per  24  hours,  having  pistons  24 
inches  in  diameter  and  a  stroke  of  10  feet. 


Fig.  16. 

Forcing  Pumps.  For  raising  water  to  a  height  greater  than 
can  be  conveniently  overcome  by  lifting,  or  when  the  discharge  is 
desired  at  a  distance  from  the  pump,  it  is  better  to  use  the  forcing 
type.  The  simple  principle  of  this  type  is  shown  in  Fig.  3.  There 
are,  however,  many  modifications  in  common  use.  It  is  usual,  if 
the  lift  to  the  pump  be  great,  to  install  a  foot  Valve  at  the  bottom 


282 


WATERWORKS  PUMPING  ENGINE  AT  CENTRAL  PARK  AVENUE  PUMPING  STATION. 
CHICAGO,  ILL. 

Worthington  pump;  capacity,  40,000,OnO  gallons  daily. 


STEAM  PUMPS  28 


of  the  suction  pipe,  as  well  a3  to  use  admission  valvas  to  the 
pump  chamber  so  that  the  suction  pipe  will  be  kept  filled  at  ail 
times,  and  the  tendency  for  the  water  to  drop  out  of  the  pump 
chamber,  while  the  suction  valve  is  closing,  be  removed. 

The  most  common  form  of  forcing  pump  is  the  doTT.ole-actino1 
piston  type  as  seen  in  Fig.  16.  As  the  piston  P  moves  to  the 
right,  it  will  create  a  suction  in  the  left-hand  end  of  the  cylinder, 
drawing  in  water  through  the  valves  AA  and  the  suction  pipe  S. 
At  the  same  time  pressure  will  be  exerted  in  the  right-hand  end 
of  the  cylinder  and  water  will  be  forced  out  of  valves  DjDj,  into 
the  discharge  chamber  and  up  the  pipe  K.  On  the  reverse  stroke, 
water  will  be  drawn  in  at  valves  AjA,  and  forced  out  of  DD. 
The  piston  must,  of  course,  be  packed  water  tight. 

As  in  the  case  of  lifting  pumps,  the  volume  to  be  raised  and 
the  speed  at  which  the  pump  can  be  run  determine  the  size  of  the 
piston;  but  the  speed  is  usually  greater  than  in  the  lifting  type. 
The  pump  must  not  be  placed  over  20  feet  above  the  level  of 
the  water  which  it  is  to  raise,  hence  for  a  high  head  the  greater 
part  of  the  lift  must  be  obtained  by  forcing  against  the  head 
above  the  pump.  It  is  a  common  rule  that  the  travel  of  a 
pump  piston  should  not  exceed  100  feet  per  minute,  and, 
taking  the.  same  problem  as  for  the  lifting  pump  this  gives, 

QO    1  f\f\ 

'     10  =  19.25  square  inches   as    the   area   of    the   piston. 
J.UU  X  -L^ 

At  the  increased  speed,  the  slip  will  be  greater,  hence  it  will 
be  necessary  to  allow  5  per  cent  or  an  area  of  19.25  X  1.05  = 
20.21  square  inches  corresponding  to  a  diameter  of  5Ja  inches. 

The  head  would  be  the  same,  hence  the  total  pressure  per 
square  inch  would  be  the  same  as  for  the  lifting  pump,  but  the 
power  would  be  increased.  The  total  force  on  the  piston  will  be 
20.21  X  8G.GO  =  1,750.1  pounds.  At  100  feet  per  minute  this 

1,750.1  X  100         ,  OA   . 
will   require  — - — „„  „„„ =  5.30   horsepower,    which   is  less 

than  before  because  the  weight  of  the  pump  rod  is  not  lifted  at 
each  stroke.  If  the  rod  be  counterbalanced  by  a  weight  at  the 
opposite  end  of  a  walking  beam,  the  lifting  pump  w.;ll  have  a 
slight  advantage  owing  to  the  smaller  slip. 

The  pump  shown  in  Fig.  16   is  doable  acting,  that  is,  it 


24 


STEAM  PUMPS 


works  on  both  strokes,  but  pumps,  especially  of  the  vertical  type, 
are  often  made  sirio-le  acting  to  suck  on  the  up  stroke  and  force  on 

t>  O  ± 

the  down ;  these  have  only  half  the  capacity  for  the  same  size  as 
the  double  acting. 

The  great  difficulty  with  the  piston  is  in  keeping  the  packing 
tight  or  of  knowing  when  it  ia  leaking;  it  is  also  difficult  to 


big.  17. 

repack  as  the  pump  must  be  dismantled  in  order  to  get  at  the 
piston.  For  this  reason  the  plunger  pump  is  often  preferred  and 
is  used  either  single  acting  with  stuffing  box  around  the  plunger 
as  in  Fig.  3,  double  acting  with  two  plungers  as  in  Fig.  17,  or 
double  acting  with  one  plunger  as  in  Fig.  18.  The  advantage  of 
this  last  over  the  piston  is  that  for  high  pressures  it  is  more  easily 
kept  tight,  and  for  gritty  liquids  the  wear  is  taken  by  the  bushing 
which  is  more  easily  and  cheaply  replaced  than  a  lining  to  the 
cylinder.  The  piston  .pump  is  more  compact;  but  the  plunger 


284 


STEAM  PUMPS 


25 


does  not  require  a  bored  cylinder  so  that  the  first  cost  la  not 
materially  different. 

The  two-plunger  pump  with  outside  yoke  is  still  larger  than 
the  single-plunger  double-acting  type  but  it  can  be  easily  repacked, 
can  be  kept  tight  against  high  pressures  and  any  leaking  is 
instantly  detected. 
For  these  reasons,  it 
is  a  favorite.  The 
double-acting  pump, 
not  only  has  greater 
capacity,  as  above 
mentioned,  but,  on  ac- 
count of  its  contin- 
uous action  produces 
a  much  steadier  flow 
than  the  single-acting 
type,  so  that  it  is  gen- 
erally  preferred. 

A  modified  form  of 
Worcester's  Engine, 
Fig.  1,  is  seen  in  the 
pulsometer  or  hydro- 
trophe,  Fig.  19,  which 
is  still  used  to  a  con- 
siderable extent  where 
extreme  simplicity  is 
desired.  The  ball  B 


Fig.  18. 


rolls  so   as    to  close 

first  A'  and  then  A; 

with  the  ball  in  the  position  shown  and  the  chamber  D  filled  with 

steam,  water  will  be  drawn  up  through  F  by  the  vacuum  caused  by 

condensation  of  the  steam.     Meantime  steam  will  enter  D'  throuo-h 

O 

A  and  force  the  water  out  through  the  check  valve  G.  This 
will  continue  until  the  steam  in  D  is  all  condensed,  when  the 
rush  of  the  water,  due  to  its  inertia,  will  drive  the  ball  valve 
B  over  against  port  A,  thus  reversing  the  action.  It  is  en- 
tirely automatic  and,  as  the  machine  is  the  acme  of  simplicity 
and  may  readily  be  made  with  large  openings,  it  will  handle  dirty 


26 


STEAM  PUMPS 


STEAM 


liquids  with  a  minimum  of  attention.  Its  usual  heat  efficiency 
is  1.2  to  1.5  per  cent,  but  this  is  not  as  objectionable  as  it  seems, 
since  small  reciprocating  steam  pumps  often  do  little  or  no  better. 
C  is  a  suction  air  chamber  connected  with  the  opening  E  to  equal- 
ize  the  flow  of  water. 

VALVES. 

Pump  valves  must  be  so  made  that  they  will  open  and  close 
quickly  and  fully  with  little  friction,  so  that  there  shall  be  no  ob- 
struction to  the  passage  of  the 
water,  yet  little  leakage  of  water 
past  the  valves  after  the  reversal  of 
motion  of  the  piston  and  before 
the  valves  have  seated.  Quick 
opening  requires  a  light  valve  with 
slight  motion,  but  quick  closing 
demands  either  a  heavy  valve  or 
a  spring  to  hasten  its  action.  In 
older  pumps  it  was  the  custom 
to  use  one  large  valve  with  a  lift 
sufficient  to  give  the  required 
passage;  the  valve  was  then  heavy 
enough  to  close  of  its  own  weight, 
but  was  clumsy  and  hard  to  fit  to 
a  seating.  In  modern  practice  the 
required  area  is  divided  among  sev- 
eral small  valves  so  that  each  one 
is  easily  and  cheaply  renewed  in 
case  of  accident  or  wear,  and  quick 
closing  is  obtained  by  the  use  of 
springs  on  the  spindles  of  the  valves. 

The  natural  classification  of  valves  is  by  the  motion  and  by 
the  method  of  securing  a  tight  joint;  according  to  the  motion  there 
would  be  division  into  flexible,  hinged,  poppet  and  ball;  according 
to  the  seating,  into  cushioned  and  ground. 

The  Flexible  valve  is  the  oldest  type,  and  is,  in  some  ways,  the 
simplest.  It  is  generally  made  of  rubber,  as  this  material  gives 
the  greatest  flexibility  with  the  hest  seating.  The  valve  is  made 
as  a  solid  disc,  the  opening  being  obtained  by  the  flexibility  of  the 


SUCTION 


Fig.  19. 


STEAM  PUMPS 


27 


Diain.  of  hole  in  center. 
Inches. 

I 


valve  itself,  and  is  usually  of  the  style  shown  in  Fig.  20.  The  seat 
is  made  with  radial  grids  to  take  the  pressure  of  the  water,  the 
openings  between  the  bars  being  made  equal  to  the  thickness  of 
the  disc;  this  thickness  depends  in  turn  on  the  diameter  of  the 
disc,  and  is  often  made  as  given  in  the  following  table: 

Diam.  of  disc.  Thickness  of  disc. 

Inches.  Inches. 

2  i 

2J 

3 

3J 

41 

58  1  H 

The  valves  of  this  type  most  commonly  used  are  the  3-inch 
and  the  4 1-inch  as  the  larger  sizes 
are  not  found  durable.  The  3-inch 
is  the  best  for  ordinary  use.  The 
hole  in  the  center  is  made  \\  to  -J 
inch  larger  than  the  spindle  to 
allow  of  free  motion ;  to  avoid  sud- 
den bending  of  the  rubber,  the 
guard  is  placed  to  give  the  disc  a 
chance  to  rise  about  -j^  inch.  When 
it  has  risen  so  far,  it  bends  around 
the  guard  and  thus  gives  a  free  Pig.  20. 

opening   for   the   passage  of    the 

water.  The  guard  should  have  a  diameter  equal  to  that  of  the 
disc  less  twice  the  thickness  of  the  disc,  and  the  radius  of  curva- 
ture should  be  equal  to  the  diameter  of  the  disc.  This  type  of 
valve  is  not  well  suited  for  high  pressures,  250  feet  head  being 
about  the  limit  for  the  ordinary  style.  If,  however,  there  are 
vanes  arranged  below  the  disc  so  that  a  rotary  motion  is  given 
to  the  valve,  it  is  found  that  there  is  no  difficulty  in  keeping  the 
valve  tight  for  heads  up  to  490  feet.  For  these  pressures,  it  is  not 
uncommon  to  use  discs  of  a  thickness  up  to  an  inch,  but  only  for 
large  sizes.  The  lap  of  the  valve  over  the  edge  of  the  seat  should 
be  from  J  to  ^  inch  according  to  the  thickness*  of  the  disc  and  the 
pressure  to  be  carried. 


287 


28 


STEAM  PUMPS 


Leather  valves  have  been  used  to  some  extent  in  the  form  of 
a  simple  flap  fastened  at  one  side  and  free  to  rise  at  the  other;  this 
makes  the  simplest  form  of  hinged  valve  and,  when  weighted  with 
a  metal  disc  on  either  side,  has  been  much  used  for  small  hand 
pumps.  It  is  not  suitable  for  severe  service. 

The  Hinged  valve,  as  its  name  implies,  is  made  to  swing  about 
a  pivot  at  one  side,  but  should  be  designed  to  lift  from  its  seat  be- 
fore it  begins  to  swing.  The  disc  is  made  of  metal  but  often  with 
a  facing  of  leather  or  rubber  for  slow  speeds;  for  high  speeds  these 
linings  will  not  stand  the  wear.  The  lift  should  be  about  J  to  J 
inch  before  the  valve  begins  to  turn  about  the  fulcrum.  The  angle 
to  which  the  valve  lifts  is  usually  made  80  degrees,  and  should 
never  be  over  60  degrees,  in  order  to  ensure  quick  opening  and 
closing.  The  motion  is  limited  by  a  stop  on  the  seat  or  on  the 
disc  of  the  valve  as  seen  in  Fig.  21.  The  hinged  valve  is  slow  in 


Fig.  21. 


Fig.  23. 


Fig.  22. 


In 


action  and  is  not  suitable  for  thick  liquors  or  high  pressures 
designing,  the  area  allowed  should  be  as  follows: 

Piston  speed,  feet  per  minute 100  125  150  175  200 

Area  of  waterway,  per  cent  of  plunger  area.  40  50  60  75  100 

For  higher  speeds  or  for  high  pressures,  it  is  best  to  use  some 
form  of  positively  driven  valve,  and,  if  such  liquors  as  sewage  or 
syrups  are  to  be  handled,  the  areas  found  from  the  above  table 
should  be  increased  about  50  per  cent. 

The  most  common  form  of  valve  in  use  at  present  is  the 
poppet  which  rises  straight  up  from  the  seat  and  gives  a  free 
opening  with  a  small  motion.  The  seat  is  made  either  flat  or  at 
an  angle  of  45  degrees  as  the  designer  may  choose,  the  beveled 


288 


STEAM  PUMPS  29 


seat  being  more  difficult  to  construct  but  retarding  the  flow  of 
water  less  than  the  flat  seat  which  necessitates  a  double  turn  in 
the  current.  The  width  of  the  beat  or  edge  of  the  seat  against 
which  the  valve  rests  is  made  J  inch  for  large  valves  and  T*6  inch 
for  small  ones.  The  flow  of  the  water  through  the  valves  should 
be  at  a  velocity  of  not  over  200  feet  per  minute,  and  the  lift  must 
be  so  proportioned  that  the  passage  by  the  valve  will  be  as  large 
as  the  area  of  the  valve  opening.  A  valve  with  flat  seat  need  not 
have  over  J  inch  lap  even  for  heavy  pressures,  but  the  joint  must 
be  carefully  made  to  avoid  leakage. 

A  common  form  of  mitre  valve  * 
is  shown  in  Fig.  22  and  of  flat  seat 
in  Fig.  23.  The  vanes  on  the  bot- 
tom of  the  disc  which  keep  the  valve 
centered  when  it  rises  are  often  given 
an  inclination  of  ^  inch  in  6  inches 
so  that  the  rush  of  the  water  will  give 
the  valve  a  rotary  motion,  removing 
all  dirt  and  keeping  the  wear  on  the 
beat  even.  For  the  flat  beat  valves 
this  is  not  always  possible  as  they 
are  closed  by  a  spring  and  the  fric- 
tion prevents  them  from  revolving. 

la  order  to  give  an  area  by  the  valve  equal  to  the  area  of  the 
seat,  the  lift  must  be  one  quarter  the  diameter  of  the  seat  opening. 
For  heavy  pressures  this  would  make  too  large  a  lift,  as  the  slip 
on  closing  would  be  excessive;  for  this  reason  the  lift  is  made  not 
over  ^  inch  and  the  number  of  valves  increased  as  may  be 
necessary.  The  seat  is  usually  made  separate  from  the  valve 
deck  and  screwed  into  place;  when  this  construction  is  used,  the 
guide  for  a  valve  (if  there  is  one)  should  be  made  a  part  of  the 
seat  so  that  the  valve  is  self  contained.  The  guides  may  be  in 
the  form  of  wings  on  "the  bottom  of  the  valve  disc,  a  spindle 
running  through  a  hole  in  the  seat  or  a  spindle  projecting 
upward  through  the  valve;  the  last  being  most  common. 

The  discs  may  be  of  metal  or  hard  rubber.  For  hot  liquids 
metal  must  be  used,  but  for  cold  liquids  hard  rubber  or  composi- 
tion is  more  common,  usually  with  a  metal  cap  to  keep  the  disc 


30  STEAM  PUMPS 


in  shape.  The  spring  used  for  closing  the  valve  should  be 
cylindrical  rather  than  conical,  as  the  strain  on  the  latter  form  comes 
largely  at  the  small  end  of  the  spring  and  the  wire  is  likely  to 
break  there.  A  design  to  be  recommended  is  that  of  Fig.  24 
which  is  described  by  Barr;  see  "Pumping  Machinery,"  p.  57. 

Double  beat  valves  and  those  with  multiple  ports  are  not 
usually  necessary  but  are  sometimes  used  for  large  work. 

Ball  valves  are  often  used  for  low  pressures.  For  these  the 
diameter  of  the  ball  is  made  1 J  times  that  of  the  beat  and  a  cage 
is  provided  BO  that  the  ball  shall  always  be 
kept  central.  The  ball  is  of  gun  metal  usually 
with  a  rubber  casing  or,  for  cold  water,  some- 
times wholly  of  rubber.  They  are  common  in 
pumps  used  for  mines  and  oil  wells  and  often 
in  connection  with  cup  leather  packings  for  the 
piston.  If  the  water  is  gritty  or  has  impur- 
ities, the  valve  seat  should  be  raised  above  the 
deck  so  that  there  will  be  room  for  the  sand  to 
settle  below  the  seat,  as  seen  in  Fig.  25. 

In  all  valves  which  have  metal  for  both  discs 
and  seats,  it  is  important  that  they  should  both 
be  of  the  same  material,  as  otherwise   there  is 
likely  to  be  galvanic  action  which  will  cause 
rapid  deterioration.     Usually,  however,  it  is  bet- 
ter  to  use  the  valve  with  a  separate  disc  of  com- 
"7^ — ~ — -*~*    position  as  this  avoids  all  possibility  of  electri- 
cal action  and  makes  ,the  refacing  of  the  valve 
unnecessary;  the  replacing  of  the  old  disc  by  a  new  one  being  all 
that  is  needed  when  the  valve  becomes  worn. 

For  valves  which  are  to  be  returned  by  a  spring,  it  is  best  to 
use  five  coils  in  the  spring  and  to  have  the  wire  of  spring  brass  of 
the  size  given 'in  the  following  table: 

Diameter  of  valve  inches 2        2|        3        3J        4        4| 

No.  of  wire  B  &  S 12      12        10      lo"        8        8~ 

In  this  style,  it  is  well  to  use  for  the  guiding  spindle  a  stud 
screwed  solidly  into  the  valve  seat  or  made  a  part  of  the  casting, 
and  fasten  the  valve  by  a  nut  at  the  top  of  the  stud,  secured  by  a 
pin.  This  ia  usually  better  than  to  use  a  stud  screwed  into  the 


200 


STEAM  PUMPS 


31 


valve  seat.  If  tho  latter  is  used,  it  is  likely  to  work  loose  and  may 
cause  much  damage  before  the  trouble  is  discovered;  it  is  also 
more  difficult  to  remove  when  repairing  fhe  valve. 

The  material  for  the  valve  depends  on  the  liquid  to  be  handled. 
For  acids  or  liquors  of  that  nature,  it  is  best  to  use  wood,  although 
it  is  not  durable,  yet  it  will  last  better  than  any  form  of  metal;  for 
salt,  petroleum  products,  and  strong  alkalies,  gun  metal  is  the  best; 
for  all  ordinary  uses,  however,  cast  iron  is  good  enough,  and  if 
used  with  composition  discs  there  will  bo  no  trouble  from  rusting 
fast  even  if  the  pump  is  idle  for  considerable  periods. 

With  respect  to  valves  for 
large  pumping  engines,  they 
are  best  made  of  double  beat 
type,  and  usually  of  the  "Cor- 
nish"  form.  For  this  a  de- 
sign used  by  Mr.  A.  F.  Nagle 
has  proven  very  satisfactory; 
it  is  shown  in  Fig.  26.  The 
features  embodied  in  this  de- 
sign are  a  small  width  of 
beat  to  avoid  any  possibility 
of  sticking  and  to  get  rid  of 
surface  on  which  the  pres- 
sure of  the  water  cannot  act 
to  open  the  valve;  a  diam- 
eter large  in  comparison  with 
the  lift  so  that  the  velocity 

with  which  the  water  comes  to  the  opening  shall  be  small;  a 
shape  which  avoids  all  sharp  curves  and  changes  of  direction  and 
all  possibility  of  air  pockets.  The  valve  has  been  found  to  embody 
all  these  qualities,  to  work  noiselessly  even  at  high  speeds,  and  to 
follow  the  motion  of  the  piston  almost  exactly. 

DESIGN  AND  CONSTRUCTION. 

The  essential  parts  of  a  reciprocating  pump  are  inlet  valves, 
a  cylinder,  a  piston  or  bucket  and  outlet  valves.  The  purpose  of 
each  is  obvious.  However,  in  order  to  get  the  best  results  certain 
points  must  be  considered  in  the  arrangement  and  construction  of 
these  parts.  Some  of  these  have  already  be*"a  mentioned  in  the 


291 


82  STEAM  PUMPS 


description  of  valves.  Admission  and  outlet  valves  are  usually  of 
the  same  construction  but  sometimes  differ  in  size,  the  outlet 
valves  being  smaller  and  more  numerous  so  that  the  lift  may  be 
less  and  the  slip  under  high  pressures  reduced.  Yalve  decks  are 
usually  arranged,  one  for  the  inlet  and  one  for  the  outlet  valves; 
into  these  decks  are  screwed  or  bolted  the  valve  seats,  as  already 
shown  in  Figs.  20 — 24,  the  valves  extending  above  into  a  valve 
chamber  as  shown  in  Fig.  1C.  The  valves  should  have  space 
enough  between  them  and  between  the  outside  valves  and  the 
walls  of  the  valve  chamber  so  that  the  area  for  the  passage  of  the 

1  O 

water  shall  equal  that  through  the  valve  openings.  Generally, 
considerations  of  strength  of  the  valve  deck  also  demand  as  wide 
spacing  as  does  the  necessary  water  way. 

The  design  of  the  cylinder  depends  entirely  on  the  kind  of 
pump;  the  considerations  involved  having  already  been  mentioned. 
For  a  small  and  compact  machine,  the  piston  type  is  the  best  and 
this  calls  for  a  smoothly-bored  barrel.  In  order  that  this  may  be 
easily  renewed,  it  is  usual  to  make  the  bored  portion  as  a  lining 
which  fits  an  outer  casting  so  that  when  worn  by  grit  or  long  use, 
the  lining  maybe  renewed  without  remaking  the  whole  water  end. 
Such  a  construction  is  shown  in  Fig.  16. 

If  there  is  much  sand  or  dirt  in  the  water,  it  is  usually  better 
to  use  some  form  of  plunger  pump,  as  the  round-turned  plunger 
is  much  cheaper  to  renew  than  the  bored-barrel  lining;  also  the 
cylinder  will  be  cheaper  as  there  is  little  boring  to  be  performed. 
The  difficulty  of  an  inside  packed  plunger  has  been  mentioned  and 
also  the  alternative  of  a  double  plunger,  outside  packed.  (See 
Figs.  17  and  18).  In  spite  of  the  difficulty  of  ascertaining  and 
stopping  leakage  past  the  piston,  and  the  expense  of  boring  and 
reboring  or  relining  the  cylinder,  the  piston  pump  is  used,  except 
for  high  pressure,  more  than  any  other  form  on  account  of  its 
compactness. 

The  bucket  is  rarely  used  except  in  vertical  pumps  and  then 
almost  entirely  for  mine  or  well  purposes.  It  is  of  the  form  of 
Fig.  25  with  possibly  the  clack  or  hinged  valve  in  place  of  the 
ball.  The  outside  of  the  bucket  is  packed  by  cup  leathers  or  by 
hemp  packing,  the  same  as  a  piston,  or  it  may  simply  have 
grooves  turned  in  the  outside  to  form  a  water  packing.  The 


STEAM  PUMPS  33 


barrel  is  often  simply  a  brass  pipe,  bored  to  make  a  fit,  and  screwed 
to  the  end  of  the  vertical  pipe  so  that  it  may  be  easily  renewed. 
In  the  case  of  deep  wells,  the  bucket  should  be  made  with  a 
long  bearing  surface  so  that  it  may  the  more  easily  keep  a  water- 
tight joint  and  may  act  as  a  steadier  to  keep  the  pump  rod  in  line. 
The  piston  rod  for  a  pump  is  made  much  larger  than  con- 
siderations of  strength  would  seem  to  demand,  in  order  that  there 
may  be  no  vibration  or  deflection,  as  these  would  make  it  almost 
impossible  to  keep  the  stuffing  box  from  leaking.  Theoretically 
the  rod  for  a  long- stroke  pump  should  be  larger  than  that  for  a 
short-stroke  of  the  same  diameter;  but,  actually,  the  margin  of 
strength  is  so  great  that  the  same  size  rod  will  answer  for  both. 
Allowance  must  be  made  in  all  cases  for  the  reduction  in 
diameter  necessary  to  fasten  the  piston  or  plunger  to  the  rod. 
This  may  be  done  by  using  a  tapered  end  fitting  a  tapered  hole  in 
the  body  of  the  piston  or  by  turning  down  the  end  of  the  rod  and 
letting  the  piston  bear  against  a  shoulder;  the  latter  method  is  the 
better.  Usually  a  nut  holds  the  piston  in  place,  the  nut  being  in 
turn  secured  by  a  lock  nut  or  split  pin  through  the  end  of  the 
rod.  Various  modifications  of  these  methods  are  of  course  used 
according  to  the  fancy  of  the  designer. 

The  diameters  of  piston  and  corresponding  rod  for  a  rod  of 
cold  rolled  steel,  tensile  strength  65,000  pounds,  a  factor  of  safety 
of  10  and  a  pressure  of  150  pounds  are  given  in  Table  IV. 

TABLE  IV. 

Piston  diam.  Rod  diam.                         Diam.  of  rod  end, 

Inches,  Inches.  Inches. 

4  If  II 

6  l|  1; 

8  II  Ij 

10  24  11 

12  2f 

14  2|  2 

The  water  end  of  the  pump  is  necessarily  long,  as  the  piston 
must  be  of  such  length  that  it  can  be  packed,  and  usually  with 
some  kind  of  soft  packing  such  as  flax,  hemp  or  leather.  Fig.  27 
shows  the  detail  of  a  piston  designed  for  use  with  square  flax  pack- 
ing; the  body  is  fastened  to  the  piston  rod  by  the  nut  A,  the  pack- 
ing laid  in  place,  and  the  follower  forced  up  by  the  nut  B  which 
;s,  in  turn,  secured  in  place  by  the  lock  nut  C.  For  large  sizes,  the 


34 


STEAM  FUMFS 


design  is  the  same  except  that  the  follower  is  set  up  by  a  number 
of  nuts  near  the  edge  screwed  onto  stud  bolts. 

The  leather-packed  piston  is  made  as  shown  in  Fig.  28.  The 
packing  is  made  by  pressing  sheets  of  wet  leather  into  iron  forms 
and  allowing  them  to  dry  there,  after  which  the  edges  are  finished, 
The  radius  of  the  corner  must  be  large,  so  that  the  leather  will  not 
be  injured  in  the  pressing  process,  about  \  to  |  inch  being  suffi- 
cient. The  diameter  of  the  disc  from  which  the  cup  is  formed 
need  not  be  more  than  1^  to  1|  inch  greater  than  that  of  the  pis- 
ton, as  there  is  no  object  in  having  the  lip  of  the  cup  longer  than 
just  sufficient  to  make  a  tight  joint. 

Less  common  forma  of  piston  packing  are  the  metal  ring 
sprung  into  place  and  the  series  of  grooves.  For  the  former,  tho 


Fig.  28. 

ring  should  bo  made  about  £-  inch  larger  ',han  the  piston  for  a  12- 
inch  piston;  other  sizes  in  proportion.  For  the  groove  packing, 
the  grooves  are  best  made  about  |  inch  deep  by  £  inch  wide.  If 
soft  packing  is  used,  the  length  of  a  piece  cut  for  a  ring  should  be 
somewhat  less  than  that  needed  to  have  the  ends  meet  when  placed 
around  the  piston  body  in  order  to  allow  for  the  swelling  of  the 
packing  as  it  becomes  wet.  One  rule  is  to  make  the  space  between 
ends  equal  to  the  width  of  the  packing. 

For  a  plunger,  a  hollow  casting  is  generally  used;  the  only 
requirement  being  that  the  thickness  shall  be  sufficient  to  with- 
stand the  pressure  against  which  the  pump  acts.  The  length  must, 
of  course,  be  equal  to  the  stroke  plus  the  length  of  the  stuffing  box 
and  an  amount  sufficient  to  ensure  that  the  head  of  the  plunger 
will  never  strike  the  gland.  A  plunger  is  sometimes  used  with  an 


STEAM.  PUMPS  85 


open  end  and  the  partition  set  back  into  the  interior  of  the  plunger, 
but  this  is  not  as  strong  a  construction  as  the  closed-end  type  and 
is  more  expensive  to  make. 

"With  single-cylinder  pumps  it  is  customary  to  use  an  air 
chamber  on  the  discharge  to  steady  the  flow  of  the  water  and  pre 
vent  shock,  but  for  those  having  several  cylinders  this  is  not  con- 
sidered  necessary.  Even  if  the  motion  is  slow,  and  the  pressure 
against  which  the  pump  works  is  great,  it  is  better 
to  use  the  air  chamber  even  with  multiple  cylinders, 
and  it  is  often  advisable  for  fast  running  pumps  or 
those  with  a  long  suction  pipe  to  use  an  air  cham- 
ber on  the  suction  side  as  well.  The  volume  of 
the  discharge  chamber  should  be  three  to  four 
times  that  of  the  piston  or  plunger  displacement 
per  stroke,  and  for  the  suction  chamber  twice  such 
displacement  if  tlio  pump  is  single.  For  duplex, 
g  to  i  less  will  answer.  The  neck  of  the  chamber 
should  be  long  and  narrow  so  that  the  air  will  not 
easily  escape,  and  the  flow  of  water  into  and  out 
of  the  chamber  will  be  somewhat  retarded.  For 
small  sizes  the  chamber  is  made  of  copper  in  a  standard  form  as 
seen  in  Fig.  29,  the  dimensions  being  about  as  follows: 

Dium.  inches.  Height,  inches.  Pipe-tap  thread,  inches. 

6  10  1 

8  14 

9  15 
10  16 

For  larger  sizes  a  casting  is  used  with  straight  sides  and  a 
hemispherical  top  as  seen  on  Fig.  IT.  For  this  style  a  common 
proportion  is  to  make  the  height  three  times  thu  diameter  and  the 
diameter  of  the  neck  one-third  that  of  the  chamber  proper. 

The  air  chamber  on  the  discharge  should  be  placed  at  the 
highest  point  of  the  valve  chest  and  above  the  delivery  opening  so 
that  the  air  will  not  tend  to  slip  out  with  the  water.  Even  then, 
the  air  will  be  gradually  absorbed  by  the  water,  and  provision 
must  be  made  for  renewing  the  air  cushion  either  when  the  pump 
is  not  in  use  by  admitting  air  through  a  cock  and  allowing  some 
water  to  escape  from  the  valve  chest,  or  continuously  by  an  auto- 
matic pump. 


STEAM  PUMPS 


The  suction  air  chamber  should  be  so  placed  that  the  stream 
of  water  flowing  to  the  pump  may  cushion  against  the  air  in  it 
without  changing  its  direction  abruptly.  Two  positions  which 
fulfill  this  condition  are  shown  in  Fig.  30.  If  it  is  impossible  to 
place  the  suction  chamber  in  such  a  position,  the  capacity  should 
be  increased  considerably,  the  amount  depending  on  the  speed  at 
which  the  pump  is  to  be  run. 

In  designing  the  valve  chest,  flat  surfaces  should  be  avoided, 
as  they  are  not  adapted  to  resist  pressure.  A  rounded  or  oval  sur- 
face gives  greater  strength  and  will  more  easily  conform  to  the 
outline  presented  by  the  valve  studs 
and  the  top  of  the  chest.  A  good 
design  is  shown  in  Fig.  16. 

Clearance  is  the  name  given  to  the 
space  at  the  end  of  the  cylinder  into 
which  the  piston  or  plunger  does  not 
travel.  It  is  not,  as  is  the  case  with 
the  steam  engine,  a  source  of  loss, 
hence  it  is  advisable  to  provide  a 
generous  amount  so  that  there  will 
be  a  place  for  grit  or  foreign  matter 
to  settle,  and  no  possible  chance  of 
the  piston  striking  the  cylinder  head. 
The  ports  or  valve  openings  and 
the  passages  from  the  valve  chests  to 


Fig.  30. 


the  cylinder  should  be  large  enough  so  that  the  velocity  of  the 
water  when  the  pump  is  working  at  its  greatest  speed  will  be 
not  over  300  feet  per  minute.  The  ports  should  be  ehort  and 
direct  to  avoid  friction,  and  if  possible  should  be  so  arranged  that 
the  water  passes  into,  through  and  away  from  the  pump  without 
changing  the  direction  of  its  motion.  This  last  condition  usually 
conflicts  with  the  necessity  of  placing  the  valves  so  that  they  are 
readily  accessible  and  is,  therefore,  disregarded  by  many  makers. 
The  stuffing-box  for  rods  1  inch  or  less  in  diameter  is  made 
with  a  cap  to  screw  over  the  end  of  the  box  and  forces  in  the  gland 
as  in  Fig.  31.  For  larger  sizes  the  gland  is  forced  in  by  nuts 
screwed  on  stud  bolts  which  pass  through  a  flange  on  the  gland.  See 
Fig.  82.  The  gland  and  box  may  be  bushed  with  brass  as  shown, 


STEAM  PUMPS 


87 


or  made  of  solid  iron.  The  box  should  be  made  deep  enough  to 
allow  four  rings  of  packing  and  should  preferably  have  the  bottom 
and  the  end  of  the  gland  chamfered  in  order  to  force  the  packing 
"against  the  rod  and  make  the  joint  more  secure. 

The  frame  or  body  of  the  pump  is  to  hold  all  parts  together 
and  keep  them  rigidly  in  position.  AVith  this  end  in  view,  it  pays 
to  use  enough  iron  to  make  the  frame  massive,  yet  it  should  be  so 
distributed  as  to  be  of  the  most  use.  The  standards  or  legs  should 
be  of  good  length  so  that  the  pump  may  stand  well  away  from  the 
foundation  and  be  accessible.  The  feet  should  have  a  large  sur- 

D 


Pig.  31.  Fig.  32. 

face  to  secure  stability  and  good  bearing.  For  pumps  which  are 
to  work  against  high  pressures,  round  chambers  connected  by 
round  passageways  should  be  used  for  the  valve  chambers.  The 
valve  chambers  should  be  so  arranged  that  the  valves  or  seats  may 
be  easily  removed  and  replaced,  a  convenient  arrangement  being 
that  of  Fig.  16  where  the  inlet  valves  are  directly  under  the  out- 
let valves,  hence  can  be  readily  examined  Details  of  such  an 
arrangement  as  used  in  the  Cameron  and  Davidson  pumps  are 
seen  in  Figs.  33  and  34  respectively. 

The  arrangement  of  the  parts  of  a  pump  is  the  test  of  a 
designer's  skill.  Air  pockets  must  be  avoided  in  the  cylinder  or 
clearance  spaces,  as  otherwise  the  pump  will  waste  much  of  its 
effort  on  the  air  thus  caught.  The  passage  through  the  cylinder 
must  be  so  designed  that  the  water  leaves  at  the  highest  point  of 
the  chamber  and  all  recesses  in  which  air  might  be  caught  must 


38 


STEAM  PUMPS 


be  carefully  avoided.  Air  pockets  in  the  discharge  valve 
chamber  are  not  serious,  but  in  the  inlet  valve  chamber  they  will 
result  in  lost  motion. 

Almost  all  small  horizontal  pumps  are  arranged  with  both  the 
inlet  and  discharge  valve  chambers  above  the  cylinder,  as  this 
makes  all  valves  readily  accessible,  and  gives  a  compact  water  end. 
Unquestionably  smoother  action  and  a  more  efficient  pump  would 
be  obtained  if  the  admission  valves  were  placed  below  the  cylinder 
so  that  the  water  need  not  reverse  its  direction  of  flow  while  pass- 
incr  through  the  pump;  but  it  is  a  case  for  judicious  compromise, 
and  the  common  arrangement  gives  good  service  so  long  as  the 

speed  of  working  is  slow. 
Nevertheless,  it  is  well  to 
keep  the  better  arrange- 
ment in  mind,  in  which  the 
suction  enters  at  the  bot- 
tom of  the  pump  and  the 
discharge  leaves  at  the  top. 
The  suction  pipe  usually 
comes  in  at  one  side,  and 


tbo  discharge  leaves  direct- 


Fig.  33. 


Fig.  34. 


ly  above  it  on  the  same  side, 
as  shown  in  Fig.  35,  or  the 
side  opposite.  Fig.  35  ia 
the  cross  section  of  a  single  cylinder  pump. 

For  the  direct-acting  steam  purnp,  the  steam  and  water 
cylinders  must  have  their  axes  coincident.  The  two  cylinders 
should  be  placed  as  near  each  other  as  is  consistent  with  provision 
for  the  valve  gear  and  room  to  care  for  the  stuffing  boxes. 
Compactness  is  desirable,  but  convenience  in  caring  for  the  pump 
and  in  making  repairs  is  much  more  essential. 

At  the  lowest  point  on  each  end  of  each  cylinder  provide  a 
drain  cock  by  means  of  which  all  water  may  be  drawn  off  when 
the  pump  is  shut  down  in  order  to  prevent  rusting  or  pitting  and 
to  avoid  danger  of  freezing  in  cold  weather. 

The  size  of  the  piston  or  plunger  and  length  of  stroke  are 
determined  by  the  capacity  desired.  The  allowable  speed  of 
piston  is  often  stated  as  100  feet  per  minute,  but  it  is  better 


298 


STEAM  PUMPS 


89 


limited  to  60  double  strokes  per  minnte,  as  the  determining 
factor  is  really  the  time  needed  for  reversal  and  changes  of  valves 
at  the  end  of  the  stroke.  For  small  pumps  the  limit  might  be 
made  100  double  strokes  per  minute,  but  the  smaller  number  is 
better.  At  60  double  strokes  or  120  single  strokes  per  miuute 
the  piston  speed  in  feet  per  minute  will  be: 


where  I  is  the  stroke  in  inches;  and  for  100  double  strokes  the 
speed  will  be  y*  times  the  above  value  or  10.7  I.  For  pumps  of 
over  6-inch  stroke  this  higher  limit  is  not  advisable. 

Table   V   gives    the    capacities    of   various   sizes   of  pump 
cylinders  at  60  double  strokes  per  min. 
ute,  without  allowance  for  slip. 

From  Table  V  can  be  seen  directly 
the  capacity  of  any  size  pump  at  a  speed 
of  60  strokes  per  minute,  or  the  diam. 
eter  and  corresponding  length  of  stroke 
needed  to  move  any  given  number  of 
gallons  per  minute.  To  find  the  capacity 
at  any  other  speed,  divide  the  given 
capacity  by  60  and  multiply  by  the 
number  of  double  strokes  at  which  the 
pump  is  to  run.  Thus  to  find  the 
capacity  of  a  pump  3  inches  diameter  by  4  inches  stroke  at  SO  double 
strokes;  the  capacity  at  60  double  strokes  is  14.7  and  at  SO  it  will  be 

19.6  gallons  per  minute. 


Fig.  35. 


The  ratio  of  stroke  to  diameter  may  be  chosen  by  the  designer, 
the  value  in  standard  designs  running  from  2:1  to  1:1.25,  the 
more  common  being  3:  2  and  1:  1. 

The  first  value  to  be  found  is  the  amount  of  water  to  be 
handled  per  minute,  and  this  will  usually  be  determined  by  the 
work  for  which  the  pump  is  to  be  used.  The  allowance  for  "slip,'* 
that  is,  the  loss  due  to  slow  closing  of  the  valves  and  leakage  must 
then  be  added  before  the  size  of  the  water  end  can  be  settled. 

The  slip  depends  on  the  style  of  valve  used,  the  size  of  pump 


STEAM  PUMPS 


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and  the  speed  at  which  it  runs.     Approximate  values  are  shown 
in  table  VI. 

TABLE  VI. 


Class  of  Pump. 

Slip  in  Percent  of  Volume  Pumped. 

At  high  speed. 

At   low   speed. 

Small  Centrifugal        

75 
50 
40 
25 
15 
8 
6 

60 
40 
30 
15 
10 
5 
4 

Medium       u          

Fire  Engines                          

Laro'e  Centrifugal 

Li  ft  and  Drainage                    

Mine  and  Deep  Well  Pumps  

Waterworks         ...        ... 

AVe  can  now  determine  the  size  of  a  pump  to  move  a  given 
volume  of  water.  Suppose,  for  example,  that  it  is  required  to 
force  200,000  pounds  of  water  through  a  condenser  per  hour. 
This,  at  8.338  pounds  per  gallon,  would  be  23,987  gallons  per 
hour,  or  400  per  minute,  if  there  were  no  slip;  but  for  a  common 
lift  pump  we  must  allow  10  per  cent  so  that  the  capacity  must  be 
for  400x1.10=440  gallons  per  minute.  From  table  V  this 
would  require  a  10  X 12,  a  9  X 14  or  an  8  X 18 ;  the  10  X 12  would 
be  the  most  common  proportion. 

The  area  of  valves  should  be  such  that  the  velocity  of  the 
water  through  them  will  not  exceed  250  feet  per  minute;  for  440 

440  X  231 
gallons,  the  volume  would  be 


1728 


=  58.8  cubic  feet.     At 


58.8 


250  feet  per  minute,  the  valve  area  =  -^  =  .2352  square  feet, 

or  practically  34  square   inches.     The  area  of  3-inch  valve  is  7 
square  inches,  so  that  the  five  valves  would  be  sufficient.     The 

circumference  is  9.42  inches;  this  gives  a  lift  of    ^ 


5  X9.4 


=  .723 


inch,  an  amount  perhaps  not  too  great  for  smooth  action  at  the  low 
pressure  of  a  condenser  pump;  but  it  would  be  better  even  for  this 
service  to  use  twelve  2-inch  valves  giving  a  lift  of  .45  inch. 

To  find  the  power  required,  it  is  necessary  to  know  the 
pressure  against  which  the  pump  is  to  act  both  for  suction  and 
forcing.  Assume  this  to  be,  in  the  present  case,  5  feet  of 


801 


42  STEAM  PDMPS 


suction  head  and  5  pounds  pressure  due  to  the  friction  in 
piping  and  condenser  tubing;  the  total  pressure  will  then  be  7.16 
pounds  per  square  inch,  and  on  the  10-inch  piston  the  total 
force  would  be  78.54x7.16  =562  pounds.  The  pump  is  to 
make  120  strokes  per  minute,  each  stroke  being  12  inches  or 
one  foot  long,  so  that  the  work  per  minute  would  be  120x562  = 
67,440  foot  pounds,  and  the  power  67,440-f- 33,000  =  2.04  horse- 
power  provided  there  were  no  friction.  It  is  customary  to  allow 
25  per  cent  for  friction  in  pumps,  which  would  increase  the  power 
required  to  2.04x1.25  =  2.55  horsepower. 

To  find  the  diameter  of  steam  piston  needed,  the  steam 
pressure  must  be  known  and  the  foregoing  process  can  then  be 
reversed.  Assume  the  pressure  to  be  80  pounds;  the  work  per 
minute  is  2.55x33,000  =  84,000  foot  pounds,  which,  at  120  feet 
per  minute  would  require  a  force  of  700  pounds,  and,  at  80 

700 

.pounds  per  square  inch  an  area  of  ^  =  8.75  square  inches,  cor- 
responding to  about  a  3|-inch  diameter.  Usually  the  steam  and 
water  ends  are  made  much  more  nearly  the  same  size  than  this 
would  indicate  and  the  steam  throttled  between  the  boiler  and  the 
steam  end  of  the  pump,  so  that  the  pump  may  be  adaptable  to  a 
wide  range  of  conditions. 

The  parts  of  a  pump  should  be  proportioned  to  withstand  the 
forces  which  are  to  come  on  them,  not  only  without  danger  of 
breaking,  but  without  bending.  For  the  parts  which  are  to  be  of 
cast  iron,  such  as  cylinder,  valve-chests  and  frame,  the  considera- 
tion which  decides  the  dimensions  is  often  the  thickness  of  metal 
which  will  cast  well;  while  for  the  piston  it  is  the  length  which 
will  give  a  good  bearing  surface  on  the  cylinder  to  resist  wear, 
and  a  tight  joint  to  prevent  leakage.  These  points  are  largely 
matters  of  experience  and  good  judgment,  but  some  ideas  can  be 
given  as  to  common  practice. 

For  a  packed  piston,  usually  4  rings  of  |-inch  square  packing 
are  used.  Common  values  of  rod  diameters  are  given  in  Table 
IV.  In  designing  the  body  and  follower  of  the  piston,  it  should 
be  remembered  that  the  less  weight  the  better  so  long  as  the 
strength  is  sufficient;  but  a  piece  of  cast  iron  less  than  g-inch 
thick  seldom  casts  well  in  any  complicated  casting. 


302 


STEAM  PUMPS  43 


For  the  cylinder,  the  same  equation  may  well  be  used  for  both 
steam  and  water  ends.  Whitham  gives,  allowing  for  strength, 
rigidity  and  possible  reboring:  £=.03j/P  D  where  P  is  the 
maximum  pressure  in  the  cylinder  in  pounds  per  square  inch 
and  D  the  diameter  in  inches;  t  is  of  course  the  thickness  of  the 
cylinder  walls.  The  length  of  the  cylinder  will  be  the  length  of 
stroke  plus  the  thickness  of  piston  and  fastening  nuts  plus  twice  the 
clearance  at  one  end  which  should  be  at  least  ^  inch.  The  clearance 
should  be  counterbored  to  leave  the  length  of  the  bore  somewhat 
less  than  the  length  of  stroke  plus  the  length  of  piston.  The  soft 
packing  or  piston  rings  should  not,  however,  be  allowed  to  run 
into  the  counterbore.  An  average  of  various  formulas  for  the 
thickness  of  cylinder  heads  and  flanges  as  given  by  Kent,  is  t  = 
.00036  P  D  +  .31  inches.  The  flanges  on  the  cylinder  are  made 
of  the  same  thickness  as  those  on  the  cylinder  head. 

For  large  cylinders  it  is  usual  to  support  the  head  by  ribs 
running  from  the  center  to  the  circumference,  though  some 
designers  consider  this  bad  practice.  The  flange  through  which 
the  bolts  pass  is  made  -|  thicker  than  the  thickness  of  heads  given 
by  the  above  formula.  To  avoid  springing  of  the  flanges,  cylinder- 
head  bolts  should  be  so  spaced  that  the  distance  on  centers  will  be 
not  over  4  to  5  times  the  thickness  of  the  flanges.  The  diameter 
should  be  such  that  the  stress  in  the  bolts  will  be  less  than  5000 
pounds  per  square  inch.  If  N  is  the  number  of  bolts  and  d  their 
diameter, 

N  X  -^-X5000  =-£jl  P,  and  simplifying, 


d  = 


5000  N 

The  area  of  inlet  and  discharge  ports  and  pipes  should  be  at 
least  equal  to  that  of  the  valves. 

The  thickness  of  the  walls  of  the  valve  chambers  is  usually 
a  little  greater  than  that  of  the  cylinder  walls.  For  high-pressure 
pumps  it  is  best  to  give  these  chambers  as  nearly  as  possible  a 
cylindrical  form  in  order  to  secure  the  greatest  strength  for  a 
given  weight  of  material. 

For  the  frame,  it  is  impossible  to  give  any  rules  or  sugges- 
tions except  that  the.  student  should  get  catalogues  from  the 


303 


44  STEAM  PUMPS 


prominent  makers  and  study  them  to  see  what  has  b*'en  found 
satisfactory. 

For  proportioning  the  driving  end  of  a  pump,  whether 
steam,  belt  or  motor  driven,  the  ordinary  rules  for  the  kind  of 
machinery  involved  apply.  However,  it  should  be  remembered 
that  the  parts  are  subjected  to  severe  shock  on  the  reversal  of  the 
pump,  hence  a  factor  of  safety  as  high  as  15  should  be  used. 

Where  pumps  are  required  for  special  service,  the  amount  of 
water  to  be  pumped  per  hour  is  generally  fixed  by  the  conditions 
of  the  service;  but  for  a  few  cases  the  method  of  determining 
that  amount  can  be  definitely  given.  For  a  boiler=feed  pump,  it 
is  necessary  to  know  the  horse-power  of  the  boilers  to  be  cared 
for  by  the  pump.  One  boiler  horse-power  will  call  for  the 
handling  of  30  pounds  of  water  per  hour,  and  the  pump  should  be 
specified  accordingly  with  an  allowance  for  good  measure.  For 
an  air  pump  to  remove  the  air  and  condensed  steam  the  amount 
of  fluid  to  be  handled  is  difficult  to  estimate,  hence,  a  common 
rule  is  to  make  the  volume  of  the  double-acting  air-pump 
cylinder  ^\-  that  of  the  low-pressure  cylinder  of  the  engine  which 
it  is  to  serve.  The  double-acting  circulating  pump  has  a  volume 
about  g'g-  that  of  the  low-pressure  cylinder,  or  it  may  be  figured 
from  the  horse-power  of  the  engine,  assuming  the  steam  consump- 
tion at  25  pounds  per  I.  II.  P.  per  hour,  and  the  cooling  water 
at  30  pounds  per  pound  of  steam.  Of  course  for  accurate  calcula- 
tion, the  steam  consumption  would  vary  with  the  size  and  type  of 
engine,  but  the  above  will  give  safe  average  values. 

Fire  pumps  are  designed  with  special  care  to  meet  the  require- 
ments of  the  insurance  companies.  Stated  briefly  these  are: 
Ability  to  start  instantly  after  long  disuse;  mast  be  duplex,  with 
cross -operated  valves;  should  preferably  be  of  plunger  pattern; 
must  be  brass-fitted  throughout;  designed  to  carry  a  water  pres- 
sure of  320  pounds;  suction  valve  area  should  be  not  less  than  50 
per  cent  of  plunger  area  for  10-inch  stroke  and  56  per  cent  for 
12-inch;  discharge  valve  area  should  not  be  less  than  f  the  sue- 
tion-valve  area;  valve  springs  should  be  cylindrical,  not  conical, 
and  held  at  the  ends  in  a  groove;  studs  to  be  so  designed  as  to 
always  allow  a  lift  J  of  the  valve  diameter;  valve  seats  should 
be  of  gun  metal  held  in  the  deck  by  a  taper  thread,  or  a  smooth 


304 


STEAM  PUMPS  45 

taper  bore  forced  in,  having  the  lower  edge  turned  over;  least  area 
of  exhaust  passage  should  be  4  per  cent  of  piston  area;  admission 
ports  should  be  not  less  than  2|  per  cent  of  piston  area;  clearances 
should  be  as  small  as  possible;  valve  tappets  should  be  non- 
adjustable;  cushion  valves  controlling  a  by-pass  from  steam  to 
exhaust  port  to  regulate  the  amount  of  steam  cushion  at  ends  of 
stroke  are  recommended  for  750  and  1000  gallon  pumps;  a  gauge 
should  be  provided  which  will  show  at  all  times  the  length  of 
stroke  that  the  pump  is  making;  water-pressure  gauge  with  J-inch 
lever  cock  should  be  connected  close  to  the  air  chamber;  a  relief 
valve  of  Ashton,  Crosby  or  similar  pattern  and  of  size  sufficient  to 
discharge  the  full  throw  of  the  pump  working  at  §  speed  should 
be  furnished  and  set  to  100  pounds  pressure;  this  valve  should 
have  a  hand  wheel  conspicuously  marked  showing  the  direction 
to  -^^opifsT^^r  5  relief  valve  should  discharge  downward  into  a 
vertical  pipe,  thence  into  a  funnel;  |-inch  brass  drip  cocks  with 
lever  handles  should  be  on  both  ends  of  the  steam  and  water 
cylinders;  a  ^-inch  lever  air-cock  should  be  on  the  cover  over  the 
water  cylinders;  each  pump  should  be  fitted  with  brass  priming 
pipe,  starting  with  a  2xlXl  inch  brass  tee  close  to  the  pump 
beneath  the  delivery  flange  and  leading  to  four  |-inch  valves,  one 
opening  to  each  of  the  four  plunger  chambers;  a  priming  tank 
should  be  provided  with  bottom  at  least  5  feet  above  the  pump, 
and  having  a  capacity  half  that  of  the  pump  in  gallons  per  minute, 
unless  water  flows  to  the  pump  under  pressure;  priming  tank 
must  be  used  only  for  that  purpose;  each  pump  is  to  be  fitted  for 
hose  connections  as  per  number  of  streams  to  be  served;  capacity 
of  cylinders,  sizes  of  piping,  air  and  suction  chambers  and  relief 
valves  should  be  as  per  Table  VII.  — 

A  special  acceptance  test  is  demanded  as  follows:  The  pump 
must  run  smoothly  and  without  slamming  at  its  full  rated  speed, 
maintaining  a  water  pressure  of  100  pounds  per  square  inch  when 
furnished  with  steam  at  a  pressure  of  45  pounds  for  the  500-gal- 
lon  pump,  50  pounds  for  the  750-gallon  pump,  55  pounds  for  the 
1000-gallon  pump.  The  water  to  be  discharged  through  IJ-inch 
nozzles  on  hose  lines  150  feet  long;  the  hose  must  lie  quiet,  show- 
ing  uniform  delivery;  with  all  water  outlets  closed  and  steam  sup. 
plied  to  give  80  pounds  water  pressure,  leakage  must  not  alW 


305 


STEAM  PUMPS 


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STEAM  PUMPS 


47 


the  pump  to  make  more  than  one  double  stroke  per  minute'  with 
water  outlets  nearly  closed  and  pump  running  slowly  it  must  carry 
water  pressure  of  240  pounds  per  square  inch  and  all  joints 
remain  practically  tight;  with  relief  valve  set  at  100  pounds  and 
all  other  outlets  closed  it  must  discharge  full  delivery  at  50  double 
strokes  per  minute  with  the  water  pressure  rising  to  not  over  125 
pounds. 

These  specifications  call  for  a  first-class  design  and  construe- 
tion,  but  such  are  necessary  if  a  fire  pump  is  to  serve  its  purpose 
of  a  protection  in  case  of  emergency. 


Fig.  36. 

A  name  plate  must  be  placed  on  the  inboard  side  of  the  air 
chamber  bearing  data  as  follows  in  black  enamel  letters  |-  inch 
high  on  a  white  enamel  ground: 

Diameter  of  cylinders  and  stroke  16x9x12.  Capacity  gal- 
lons per  minute  750  or  three  1  J-inch  smooth  nozzle  streams.  Full 
speed, 'revolutions  or  double  strokes.  "For  Fire  purposes  never 
let  steam  get  below  50  pounds,  nights  or  Sundays." 

TYPES. 

In  classifying  pumps  by  types,  two  methods  of  division 
naturally  suggest  themselves;  the  first  according  to  the  arrange- 
ment of  the  water  end,  the  second  according  to  the  means  of 
Driving  employed.  The  difference  between  single-acting  and 


807 


48  STEAM  PUMPS 


double-acting  pumps  has  already  been  noted;  the  single,  duplex 
or  triplex  arrangement,  depends  on  whether  one,  two  or  three 
cylinders  are  assembled  into  a  single  machine,  drawing  water 
from  the  same  suction  inlet  and  discharging  it  into  the  same 
outlet. 

The  single  pump  is  much  used  for  small  sizes  or  where  con- 


stancy of  flow  is  of  minor  importance.  It  is,  of  course,  the 
cheapest  arrangement  and  gives  satisfactory  results  if  the  pump 
is  of  ample  size  for  the  work.  A  difficulty  with  this  type  of 
pump  is  the  provision  of  a  means  of  operating  the  steam  valve  to 
reverse  the  motion  of  the  piston  at  the  end  of  the  stroke.  The 
pistons  in  steam  and  water  cylinders  must  be  stopped  gradually  to 
avoid  pounding,  and  this  leaves  no  force  available  just  at  the  end 
of  the  stroke  when  it  is  needed  to  move  the  steam  valve  so  as  to 
reverse  the  motion. 

The  difficulty  has  been  overcome  in  two  ways;  first  by  the 
introduction  of  a  shaft  and  fly  wheel,  driven  by  a  crank  and  a 
yoke  in  the  rod  between  the  steam  and  water  cylinders  a*  seen  in 
Fig.  30.  The  inertia  of  the  fly  wheel  then  furnishes  the  force 
needed  to  move  the  valve  at  the  instant  of  reversal,  generally  by 


308 


STEAM  PUMPS  49 


means  of  an  eccentric  on  the  shaft.  This  form  is  often  used  for 
fire-engines,  two  or  three  sets  of  cylinders  sometimes  being 
counec£ed  to  one  shaft,  in  which  case  the  pump  becomes  of 
duplex  or  triplex  form.  For  stationary  pumps,  the  fly  wheel  and 
shaft  are  more  commonly  placed  beyond  the  cylinders  at  one  end 
of  the  frame,  and  the  shaft  is  driven  by  a  crank  and  connecting, 
rod  mechanism  from  a  crosshead  attached  to  the  piston  rod  as 
seen  in  Fig.  37.  The  fly  wheel  also  makes  it  possible  to  use 
steam  expansively.  The  second  method  of  effecting  reversal  is 
by  the  use  of  an  auxiliary  valve  and  steam-driven  main  valve. 
This  is  the  system  generally  found  on  small,  single-cylinder, 
direct-acting  pumps  for  boiler  feeding,  tank  filling  and  similar 
uses.  The  details  of  the  devices  used  vary  greatly  with  different 
makes ;  these  will  be  taken  up  later. 

The  single  pump  is  compact,  cheap  and  convenient,  but  the 
flow  of  water  is  by  a  series  of  impulses  rather  than  in  a  steady 
stream,  so  that,  if  the  pump  is  forced,  it  slams  badly  and  produces 
water  hammer,  an  evil  but  partially  remedied  by  the  use  of 
discharge  and  suction  air  chambers. 

Duplex  pump.  To  avoid  this,  and  at  the  same  time  to 
simplify  the  moving  of  the  steam  valve,  the  late  Henry  II. 
Worthington  devised  the  duplex  form,  in  which  two  direct-acting 
pumps  are  mounted  side  by  side,  the  water  ends  and  the  steam 
ends  working  in  parallel  between  inlet  and  exhaust  pipes  as  seen 
in  Fig.  38.  The  steam  valve  for  cylinder  A  is  moved  by  a  bell- 
crank  lever  driven  from  the  rod  of  cylinder  B  as  it  nears  the  end 
of  its  stroke;  so  that,  when  the  piston  of  B  is  about  to  come  to 
rest,  that  of  A  is  set  in  motion.  While  the  piston  of  A 
makes  its  stroke,  that  of  B  is  at  rest  until  that  of  A,  near  the  end 
of  its  stroke,  moves  the  steam  valve  of  cylinder  B  by  means  of  a 
second  bell-crank  lever,  and  the  piston  of  B  is  once  more  set  in 
motion.  Thus  the  pistons  move  alternately,  but  one  or  the  other 
is  always  in  motion  and  the  flow  of  water  is  made  practically 
continuous.  By  this  arrangement  the  auxiliary  steam  valve  is 
made  unnecessary  and  a  simple  D  valve,  driven  by  a  valve  rod 
rurning  through  a  stuffing  box,  is  used. 

The  triplex  pump  having  three  cylinders  delivering  to  the 
same  outlet  is  generally  used  for  power  pumps;  the  pistons  or 


309 


50 


STEAM 


plungers  are  driven  from  a  shaft  by  three  crajiks  or  eccentrics,  set 
at  120  degrees  to  each  other  so  that  the  turning  effort  required  on 
the  shaft  may  be  as  uniform  as  possible  and  the  flow  of  water 
steady.,  A  style  often  used  is  single-acting  with  trunk  plungers, 
that  is,  the  connecting  rod  which  drives 
the  plunger  is  fastened  to  a  pin  inside 
the  hollow  body  of  the  plunger  as  seen 
in  Fig.  39.  This  gives  a  compact  form 
and  one  not  likely  to  get  out  of  order, 
but  the  trunk  arrangement  is  inconven- 
ient in  case  of  any  wear  on  the  pin  in- 
side the  plunger,  and  the  side  thrust  of 
the  connecting  rod  creates  a  certain  tend- 
ency to  wear  the  plunger  packing  so  that 


Fig.  38. 

It  will  not  remain  tight.  On  the  whole  it  is  better,  though  more 
expensive,  to  have  a  regular  crosshead  and  ways  to  receive  the 
thrust  of  the  connecting-rod  as  in  Fig.  42.  The  cylinders  in  this 
style  of  pump  are  usually  vertical  and  the  crank  shaft  is  driven 
through  a  pair  of  reducing  gears  from  a  second  shaft  which  is,  in 
turn,  driven  by  a  pulley  and  belt  or  an  electric  motor. 

Methods  of  Driving.     With  respect  to  the  method  of, driving, 
the  most  common  type  of  pump  is  the  direct-acting,  steam-driven, 


810 


STEAM  PUMPS 


with  steam  piston  and  water  piston  or  plunger  on  opposite  ends 
of  the  same  rod.  For  small  sizes,  the  steam  cylinder  works  with- 
out  expansion  of  steam,  the  piston  being  driven  by  full  boiler 
pressure  throughout  the  stroke.  In  fact  it  is  impossible  to  avoid 
this  feature  of  full-stroke  admission,  since  the  pressure  in  the 
water  end  is  constant  throughout  the  stroke,  unless  some  means, 
such  as  a  fly  wheel  or  accumulator,  be  provided,  a  complication 
which  is  undesirable  with  small  powers.  The  simplest  way  to 
make  any  use  of  the 
expansive  force  of  the 
steam  is  by  compound, 
ing;  that  is,  letting 
the  steam  exhaust 
from  the  small,  high- 
pressure  cylinder,into  ff 
which  it  is  first  ad-  I  I  It 
mitted,  to  a  larger  /  /  /ft 
low-pressure  cylin-  W 

der,  placed  in  tan-  \  I  lr 
dem,  with  the  first  \\  \ 
one.  See  Fig.  40.  \O/^ 
This  arrangement  V 

gives  a  pressure  on 
the  low-pressure  pis- 
ton, which  gradually 
decreases  from  the  be- 


ginning to  the  end  of 
the  stroke  while  the 
pressure  on  the  high-pressure  piston  is  constant,  so  that  what- 
ever  useful  work  is  gained  from  expansion  is  in  the  low-pres- 
sure cylinder.  This  is,  however,  found  to  be  sufficient  to  pay 
for  the  extra  cost  if  the  service  is  continuous,  in  sizes  having 
a  water  cylinder  over  8x12  inches.  The  compound  pump  is  nearly 
always  duplex,  though  a  few  manufacturers  offer  a  single  tandem- 
compound  style.  Since  the  steam  pistons  must  move  together, 
the  steam  valves  must  move  together,  and  a  single  motion  serves  to 
operate  the  valves  for  both  high  and  low-pressure  cylinders. 


Fig.  39. 


311 


52 


STEAM 


STEAM  PUMPS  53 


The  simple  steam-driven  pump  requires  from  CO  to  120 
pounds  of  steam  per  horse-power,  per  hour;  the  gain  bj  compound, 
ing  is  about  30  per  cent  per  100  pounds  increase  in  boiler  pressure, 
so  that  the  steam  consumption  will  be  40  to  95  pounds  per  horse- 
power hour. 

The  volume  of  the  low-pressure  cylinder  is  made  from  2  to  4 
times  that  of  the  high-pressure,  depending  on  the  initial  pressure 
to  be  used. 

The  large  steam  consumption  of  direct-acting  pumps  of  the 
single-cylinder  type  has  led  to  the  adoption,  in  many  large 
stations,  of  power-driven  pumps  of  various  kinds.  It  is  probably 
true  that  the  cost  for  steam  is  less  by  this  method  when  the  power 
is  developed  by  large  engines,  even  after  the  losses  in  transmission 
are  accounted  for,  because  the  efficiency  of  the  engine  is  so  much 
greater  than  that  of  a  small  pump.  But,  for  small  plants,  the 
convenience  of  having  the  pump  located  near  its  work  and  of 
being  able  readily  to  control  the  speed  has  overbalanced  the  con- 
sideration  of  saving. 

As  previously  mentioned,  nearly  all  power  pumps  are  geared, 
the  power  being  applied  to  a  driving  shaft  as  seen  in  Fig.  39. 
The  belted  type  is  driven  from  a  countershaft  and  provided  with 
fast  and  loose  pulleys  used  for  starting  and  stopping,  but  there  is 
usually  no  means  of  speed  regulation.  This,  together  with  the 
expense  of  belting,  the  room  needed  and  the  fact  that  the  con- 
venient  location  for  a  pump  is  likely  to  be  such  as  to  make  a  belt 
a  nuisance  have  prevented  a  general  use  of  this  type,  and  with  the 
general  introduction  of  electric  power  into  all  plants,  the  motor- 
driven  pump  is  superseding  it. 

The  motor-driven  pump  is  of  the  same  general  form  as  the 
belted,  but  has  an  electric  motor  mounted  on  the  driving  shaft  in 
place  of  the  pulley,  or  has  a  double-reduction  gearing  as  in  Fig. 
41.  The  high  speed  at  which  motors  run  make  this  double 
reduction  necessary  except  in  the  case  of  large  pumps.  The  only 
alternatives  are  the  use  of  a  large,  slow-speed  motor  or  a  belted 
motor,  either  of  which  would  be  cumbersome  and  expensive.  As 
to  efficiency,  probably  there  is  not  much  difference  between  the 
belted  and  the  motor-driven  types.  The  electric  method  of  trans- 
mitting  power  from  the  ermine  to  the  pump  will  be  more  econom- 


313 


54 


STEAM  PUMPS 


ical  than  belting,  but  the  tiansformation  in  the  motor  and  the 
loss  in  the  extra  set  of  gears  will  offset  this. 

The  speed  of  the  motor  can,  however,  be  controlled  by  a 
starting  box,  or  rheostat  in  the  field  circuit,  hence  the  motor- 
driven  has  a  considerable  advantage  over  the  belted  type. 


Pig.  41. 

As  compared  with  the  direct-acting  type  the  economy  would 
be  about  like  this: 

Direct-acting—steam  consumption,  average,  90  pounds  per  hour  per 
H.  P. 

Belt-driven — steam  consumption  of  engine,  per  B.  H.  P,  hour,  average 
35  pounds;  at  an  efficiency  of  trans- 
mission for  belting  of  70  per  cent  and 
for  gearing  of  85  per  cent,  this  would 
require  about  59  pounds  of  steam  per 
hour  per  H.  P.  delivered  to  the  pump 
and  at  an  efficiency  of  75  per  cent  for 
the  pump  this  would  give  about  78 
pounds  of  steam  p*»*  hour  per  H.  P. 
of  effective  work. 

Motor-driven — steam  consumption  as  before,  35  pounds;  efficiency  of 
dynamo  93  per  cent,  of  transmission 
90  per  cent,  of  motor  93  per  cent,  of 
gearing  72  per  cent,  of  pump  75  per 
cent,  gives  a  steam  consumption  per 
effective  H.  P.  of  83  pounds  per  hour. 

Of  course  with  large  units  the  efficiencies  may  be  better,  but 
the  relation  would  be  about  the  same.  The  greater  convenience 
of  the  direct-acting  pump  as  to  size  and  mean*  of  control,  and  the 


314 


II 


(A    9 

if 


il 


STEAM  PUMPS 


ability  to  start  it  when  the  engine  is  not  running  have  weighed  in 
its  favor  in  the  majority  of  cases. 

For  some  few  places  a  gas  or  oil  engine  has  been  used  for 
pump  driving.  In  this  typo  a  clutch  must  be  introduced  between 
the  engine  and  the  pump,  Fig.  42,  as  the  engine  will  not  start 
under  load.  The  engine  must  first  be  started,  then  the  pump 
thrown  on  empty  and  finally  the  valves  operated  so  that  the  pump 
will  begin  to  work.  There  is  no  means  of  varying  the  speed,  but 
a  regulator  is  sometimes  introduced  which  throws  out  the  clutch 
when  the  water' reaches  a  certain  height  in  the  tank  or  reservoir 


Fig.  42. 

to  bo  filled.  This  type  is  used  only  for  such  service  as  water  sup- 
ply for  a  house  or  reservoir  system,  and  would  hardly  bo  desirable 
elsewhere. 

To  economize  in  floor  space,  the  vertical  marine  typo  of  pump 
is  used.  This  is  generally  duplex,  but  occasionally  single,  and 
except  for  the  vertical  arrangement  is  identical  with  the  hori- 
zontal type. 

Another  special  type  is  the  combined=condenser  pump,  Fig. 
43,  in  which  the  steam  cylinder  is  placed  in  the  center  and  drives 
on  one  end  of  the  piston  rod  a  vacuum  pump  for  drawing  the  con- 
densed steam  and  air  from  the  condenser,  and  on  the  other  end  a 


315 


56 


STEAM  PUMPS 


pump  for  forcing  the  cooling  water  through  the  condenser  tubes. 
The  steam  cylinder  is  the  same  as  for  any  single  pump  except 
that  there, is  a  stuffing  box  at  each  end;  the  water  end  is  the  same 
as  for  any  pump;  but  the  air-pump  end  lias  composition  disc 


Calves  with  an  area  of  opening  larger  than  that  for  a  water 
cylinder  of  the  same  size,  and  the  springs  which  close  the  valves 
are  set  at  a  less  tension  than  for  water. 

Air  pumps  of  special  forms  for  condensers  are  often  used 
combined  with  the  condensers;  they  are  driven  by  a  separate 
engine  or  by  a  bell-crank  lever  from  the  crosshead  of  the  main 


316 


STEAM  PUMPS 


5? 


engine.     The  cylinders  are  often  vertical  and  sinrrln-actino-  On  tho 

v3  "  d  ?D 

lifting  principle  with  valves  in  the  top  of  the  bucket.  A  unique 
and  in  some  ways  commendable  style  is  that  of  Fig.  44  which 
avoids  inlet  valves  and  valves  in  the  bucket,  yet  removes  both  air 
and  the  water  of  condensation  quickly  and  effectively.  Con- 
densed steam  and  air  flow  into  the  lower  recess  A  through  the 
passage  B  from  the  condenser;  as  the  piston  descends,  it  forces 
the  water  from  A  so  that  it  shoots  up  in  the  direction  indicated 
by  the  dotted  lines  through  the  ports  p T>  i'lto  the  cylinder  C. 
The  piston  rising,  closes  ports  p X>  an(l  catches  the  water  and  air 
in  the  cylinder  forcing  them  out 
through  the  valves  v  in  the  top 
into  the  discharge  chamber  3)? 
whence  the  mixture  escapes 
through  the  exhaust  passage  K 
to  the  hot  well,  or  wherever  may 
be  desired. 

For  certain  uses,  such  as  keep- 
ing up  the  pressure  on  a  hy- 
draulic elevator  system,  drain- 
ing a  pit  or  maintaining  the 
water  level  in  a  tank,  it  is  essen- 
tial to  have  an  automatic  method 
of  control  which  shall  start  and 
stop  the  pump  as  may  be  needed. 
For  direct-driven  steam  pumps 
this  is  accomplished  by  control  of  a  damper  valve  or  a  quick- 
acting  gate  placed  in  the  steam  pipe  and  for  the  motor-driven 
pump  by  a  switch  on  the  starting  resistance  box.  In  the  one 
case,  a  iloat  is  moved  with  the  water  level,  in  the  other  a  dia- 
phragrn  worked  by  the  tank  pressures  actuates  a  series  of  levers 
as  seen  in  Fin-.  41  so  as  to  work  the  steam  valve  or  switch  as  the 

O 

case  may  be. 

For  high  pressures  and  high  speeds  what  is  known  as  the 
Riedler  System  of  mechanically  operated  valves  (Fig.  45)  is  found 
especially 'desirable.  The  valve  is  of  the  poppet  type,  made  so 
large  that  one  valve  answers  for  each  end  of  a  cylinder  and  is 
opened  and  closed  by  a  rocking  arm  N,  turned  by  a  link  and 


Fig.  44. 


317 


STEAM  PUMPS 


driven  from  a  wrist-plate  much  as  in' a  Corliss-engine  valve  motion. 
The  mechanical  driving  permits  a  high  lift,  with  rapid  opening 
and  closing  at  the  end  of  the  stroke,  thus  decreasing  the  slip  and 
shock.  The  high  lift,  1  to  2  inches,  and  large  water  passages 
decrease  the  friction  while  the  mechanical  operation  of  the  valves 
also  allows  of  tho  high  piston  speed  necessary  to  secure  economy 
in  steam  consumption. 

Referring  to  Fig.  45,  the  valve  body  P  has  on  its  lower  face 


Fig.  45. 

a  leather  seal  S  secured  by  a  plate  O.  The  sleeve  D  works  on  the 
spindle  13,  raised  by  a  pin  in  the  arms  K  which  passes  under  the 
collar  II  and  is  lowered  by  the  pressure  of  the  blocks  J  on  the 
cushion  plate  G.  F  is  a  rubber  buffer  to  take  the  shock  in  case 
an  obstruction  gets  into  the  valve.  The  arms  K  are  mounted  on 
and  turned  by  a  spindle  which  passes  through  the  bushing  C  and 
is  rotated  by  the  crank  L  and  crank  pin  N.  One  valve  is  used  for 
inlet  and  one  for  outlet  on  each  cylinder,  as  seen  in  the  right-hand 
plunger  of  Fig.  40;  for  the  left-hand  end,  the  outlet  valve  of  the 
larger  plunger  acts  as  an  inlet  and  the  clack  valve  between  passages 


818 


STEAM  PUMPS 


59 


HI  9 


60  STEAM  PUMPS 


C  and  D  acts  as  an  outlet  valve.  The  differential  type  of  pump 
here  shown  is  used  for  high  pressures  and  to  give  a  continuous 
flow  with  few  valves;  the  cross-section  of  plunger  II  (Fig.  40),  is 
half  that  of  J,  hence,  on  the  stroke  towards  the  left,  half  the  water 
discharged  by  J  is  thrown  into  the  small  plunger  chamber  and 
half  into  the  passage  D;  on  the  stroke  towards  the  right,  the  half 
which  entered  the  small  plunger  chamber  is  driven  into  chamber 
D  and  the  large  plunger  draws  its  full  quantity  through  the  suc- 
tion pipe  B.  The  large  passages  and  valves,  the  ample  discharge 
and  suction  air-chambers,  together  with  the  positive  opening  of  the 
valves,  combine  to  make  this  pump  very  efficient  and  quiet  in  run- 
ning. However,  it  requires  a  large  space  in  proportion  to  its 
capacity  while  its  complexity  makes  it  expensive,  bo  that  it  is 
available  only  for  large  sizes  and  in  places  where  the  space  occu- 
pied is  not  of  special  importance. 

STEAM  VALVES. 

The  simplest  form  of  valve  is  that  used  with  a  fly-\vheel 
pump  and  which  is  moved  by  an  eccentric  as  seen  in  Fig.  37;  the 
detail  is  shown  in  Fig.  47  and  the  action  as  follows: 

AVith  the  valve  v  in  the  position  showrn,  steam  is  flowing 
through  the  port  a'  into  the  right-hand  end  of  the  cylinder  and 
forcing  the  piston  towards  the  left;  at  the  same  time,  any  steam 
which  may  be  in  the  left-hand  end  of  the  cylinder  is  driven  out 
through  the  port  a  into  the  exhaust  passage  1)  and  thence  to  the 
exhaust  pipe.  If  the  shaft  M  be  turning  as  indicated  by  the 
arrow,  the  eccentric  e  which  is  keyed  to  it,  will  also  turn,  and 
sliding  in  the  eccentric  strap  S  will  draw  it  towards  the  right, 
and  with  it  the  valve.  When  the  eccentric  has  made  a  fourth  of 
a  revolution  it  will  be  vertically  above  the  shaft,  and  will  have 
drawn  the  valve  over  so  that  it  covers  both  ports,  while,  at  the 
same  time  the  piston  will  have  moved  so  that  it  will  stand  at  its 
extreme  left-hand  position.  As  the  motion  continues,  the  left- 
hand  port  <?,  will  be  opened  to  steam  and  the  port  a'  to  exhaust, 
causing  the  piston  to  reverse  and  move  towards  the  right,  which 
will  continue  until  the  eccentric  has  moved  the  valve  to  its  extreme 
right-hand  position  and  back  to  cover  both  ports.  The  eccentric 
standing  directly  below  the  shaft,  the  piston  will  again  reverse  and 
start  towards  the  left,  and  the  cycle  be  repeated. 


320 


STEAM  POMPS 


61 


This  style  of  valve  is  called  the  D  valve,  and  is  much  used  for 
pumps  and  for  the  smaller  reciprocating  steam  engines.  For  the 
ordinary  pump  the  valve  is  made  so  that  when  in  mid  position 
it  just  covers  the  ports,  and  steam  will  enter  one  or  the  other  end 
of  the  cylinder,  if  the  valve  is  moved  from  that  position.  Steam 
will  then  be  admitted  full  stroke  and  work  without  expansion  in 
the  cylinder.  If  it  is  desired  to  utilize  some  part  of  the  expansive 
force  of  the  steam,  "  lap  "  must  be  added  to  the  valve  as  shown  at 
a,  Fig.  48,  so  that  the  port  may  be  closed  before  the  piston  reaches 


Fig.  47. 

the  end  of  the  stroke;  then  the  eccentric  must  be  turned  forward 
on  the  shaft  in  the  direction  of  its  motion  in  order  that  the  valve 
may  open  by  the  time  the  piston  is  ready  to  reverse,  and  then  "  in- 
side  lap,"  £,  must  be  adjusted  so  that  the  exhaust  port  will  neither 
open  too  soon,  thus  wasting  the  expansive  energy  of  the  steam,  nor 
close  too  early,  thus  causing  too  great  a  compression  of  the  steam 
caught  between  the  piston  and  the  end  of  the  cylinder. 

The  construction  is  the  same  as  for  a  simple  reciprocating 
engine,  which  indeed  it  is,  with  the  addition  of  a  pump  cylinder 
and  piston  attached  to  the  end  of  the  piston  rod. 

Another  form  of  valve  common  in  pumps  is  the  B  type,  Fig. 
49,  The  action  is  the  same  as  for  the  D  type,  except  that  steam 


321 


63  STEAM  PUMFS 


flows  into  the  cylinder  through  the  cup-shaped  cavity  in  the  valve 
instead  of  past  the  end,  and  the  motion  of  the  valve  relative  to  that 
of  the  piston  is  the  opposite  of  that  for  the  D  valve.  The  B  type 
is  adapted  for  use  with  the  steam-driven  valve  to  be  described,  but 
is  not  suited  to  be  driven  by  an  eccentric.  The  steam-driven  valve 
is  used  on  the  great  majority  of  small  single  pumps  on  account  of 
the  compactness^  light  weight  and  low  cost  and  in  spite  of  the  poor 
steam  economy.  In  a  few  of  the  first  named  pumps,  for  instance, 
the  early  Worthington,  single  type,  the  main  steam  valve  was 
moved  by  tappets  on  the  valve  rod  which  were  struck  by  an  arm 
fastened  to  the  piston  rod.  This  was  not  certain  in  its  working 
and  has  been  displaced  by  the  main  valve  moved  by  a  small  piston 


Fig.  48.  Fig.  49. 

working  in  an  auxiliary  cylinder.  Steam  is  admitted  to  this 
cylinder  by  an  auxiliary  valve  moved  by  a  tappet  or  lever  mechan- 
ism worked  from  the  main  piston  rod. 

The  designs  of  different  makers  vary  more  in  this  detail  than 
in  any  other,  and  we  shall  now  discuss  a  few  typical  examples  at 
some  length. 

The  first  to  be  developed  was  the  Knowles,  Fig.  50.  The 
chest  piston  A  is  moved  by  steam  admitted  through  ports  in  and 
2  between  the  end  of  the  chest  piston  and  its  cylinder,  and  carries 
with  it  the  main  steam  valve  B,  which  opens  and  closes  the  ports 
to  the  main  steam  cylinder.  The  ports  so  y  z  and  of  y'  z',  of  the 
small  detail  view,  are  made  to  register  with  the  ports  m  n  and 
tn'  n'  by  the  turning  of  the  chest  piston  by  the  tappet  C  driven  by 
the  rocker-bar  R  and  the  roller  E.  As  the  main  piston  reaches 
its  left-hand  position,  the  roll  E  will  lift  the  left-hand  end  of  the 
rocker  bar  and  place  the  ports  so  that  steam  is  admitted  to  the 
right  of  the  chest  piston  and  exhausted  from  the  left;  the  main 
valve  will  then  be  carried  to  the  jx>sition  shown  in  Fig.  50  and 


STEAM 


63 


steam 'be  admitted  to  the  left-hand  end  of  the  main  steam  cylinder  in 
order  to  drive  the  main  piston  towards  the  right.  At  the  other 
end  of  the  stroke  the  operation  will  be  reversed.  The  arm  F  will 
not  strike  tappets  C  or  D  unless  the  steam  fails  to  move  the  maiu 
valve,  in  which  case  the  piston  A  would  be  driven  by  pressure  on 
the  tappets,  but  with  more  or  less  slamming  depending  on  the 


Fig.  50. 

The  third  set  of  ports  in  the  chest  piston  and  its  seat  are  to 
form  a  connection  between  the  two  ends  of  the  auxiliary  cylinder 
after  the  chest  piston  has  moved  a  certain  distance  in  order  to  pre- 
sent its  striking  the  end  of  the  chest.  The  length  cf  stroke  can 
be  changed  by  altering  the  height  of  the  roller  E,  and  unevenness 
of  stroke  at  the  ends  can  be  remedied  by  changing  the  length  of 
the  link  L. 

An  entirely  different  style  of  valve  is  that  of  the  Cameron 
pump,  Fig.  51.  F  is  the  valve-piston  which  drives  the  valve  G. 
by  means  of  a  projection  which  sticks  up  through  the  neck  of  the 


323 


64 


STEAM  PUMPS 


piston.  The  ends  of  the  valve  piston  are  hollow  as  shown  in  the 
cross-section  of  the  right-hand  end,  and  a  small  hole  P,  at  each 
end  admits  steam  at  full  pressure  to  the  ends  of  the  chest  cylinder. 
If  the  main  piston  C  is  moving  to  the  left  ^as  it  would  be  with 
the  valve  G  in  the  position  shown),  when  it  reaches  the  end,of  the 
stroke,  it  will  strike  the  reversing  valve  I'  and  force  it  open,  thus 
allowing  the  steam  at  the  left  of  the  valve  piston  to  flow  into  the 
exhaust  port  through  the  passage  E'.  The  steam  at  the  right, 
hand  end  cf  the  valve  piston  will  expand,  forcing  the  piston  F  to 


Fig.  51. 

the  left  and  carrying  valve  G  with  it,  thus  opening  the  right-hand 
end  of  the  main  cylinder  A  to  the  exhaust  and  the  left-hand  end 
to  live  steam,  which  will  reverse  the  motion  of  the  piston  C. 
As  the  valve  piston  moves  to  the  left,  it  will  cover  and  close 
the  port  E'  hence  will  be  brought  to  rest  without  shock  by  the 
cushioning  of  the  enclosed  steam.  As  soon  as  the  piston  C  leaves 
it,  the  reversing  valve  I'  will  be  closed  by  the  pressure  in  the 
passage  K'  which  is  iilled  with  live  steam.  At  the  other  end  of 
the  stroke,  the  same  series  of  operations  follows  by  the  action  of 
the  reversing  valve  I. 


324 


STEAM  PUMPS 


65 


The  valves  require  no  adjustment  and  are  easily  brought  to  a 
new  seat  when  they  become  worn,  by  removing  the  bonnets.  If 
piston  F  becomes  worn  after  long  service,  the  cylinder  may  be 
re-bored  and  bushed  or  the  holes  P  may  bo  drilled  a  little  larger, 
which  will  give  greater  pressure  in  the  end  of  the  chest  cylinder 
and  keep  the  pump  working  steadily  for  a  long  time  even  with 


Fig.  52. 


the  piston  F  considerably  worn.  II  is  a  starting  lever,  worked  by 
a  handle  outside,  for  use  in  case  the  pump  should  stop  with  the 
valve  G  covering  both  admission  ports. 

A  third  style  of  valve  is  shown  in  Fig.  52,  that  of  the  Deane 
of  Holyoke.  In  this  the  auxiliary  valve  is  in  the  form  of  a  yoke 
surrounding  the  main  valve;  the  working- valve  seat  and  ports  for 
the  auxiliary  are  at  one  side  of  the  main-valve  seat,  and  the  ports 
supply  steam  to  or  exhaust  it  from  the  ends  of  the  valve- piston 


825. 


6TEAM  PUMPS 


chamber  through  openings  in  the  end  of  the  pi&ton.  The  auxiliary 
valve  is  moved  by  a  valve  rod  actuated  by  tappets  and  a  series  of 
levers  from  the  main  piston  rod.  If  the  valve  piston  fails  to  move 
the  main  valve,  the  auxiliary  valve,  acting  as  a  yoke,  will  finally 
drive  the  main  valve  over,  by  positive  action. 

A  somewhat  similar  device  ia  used  on  the  Dean  Bros',  pump, 
Fig.  53.  There  is,  however,  no  period  of  rest  of  the  auxiliary 
valve,  the  motion  being  similar  to  that  given  by  an  eccentric,  and 
there  is  no  provision  for  moving  the  main  valve  other  than  by  the 
valve  piston,  because  the  positive  driving  of  the  auxiliary  valve 


Fig.  53. 

makes  this  unnecessary.  The  auxiliary  valve  F  works  on  a  seat 
G  on  the  side  of  the  valve-piston  cylinder,  being  driven  by 
the  rod  A  and  the  rocker  arm  II  from  the  main  piston  rod  P. 
The  length  of  its  stroke  can  be  changed  by  moving  the  pin  B  in 
the  slot  of  the  rocker  arm,  and  the  stroke  of  the  main  piston  will 
thus  be  changed.  The  main  valve  is  of  the  D  form  with  a  pro- 
jection from  the  top  which  is  engaged  by  the  valve  piston;  the 
ports  enter  the  cylinder,  as  in  practically  all  direct-driveo  steam 


GSG 


STEAM  PUMPS  67 


pumps,  at  some  distance  from  the  end ;  thus  steam  will  be  caught 
to  form  a  cushion  for  the  piston  at  the  end  of  the  stroke. 

The  auxiliary  valve,  Fig.  53,  is  made  very  short  and  is  so 
arranged  that  its  ports  are  open  only  when  the  main  piston  is  near 
the  end  of  its  stroke.  Ports  b  I'  are  for  admission  of  live  steam 
and  port  c  is  for  exhaust.  All  three  ports  are  covered  by  the 
valve  except  when  near  the  end  of  its  travel;  then  the  groove  d  in 
the  face  of  the  valve  connects  ports  J  and  c  and  allows  the  steam 
to  exhaust  from  the  left-hand  end  of  the  valve  piston  while  port  I' 
is  uncovered  and  live  steam  is  admitted  to  the  right-hand  end;  or, 
at  the  opposite  end  of  the  stroke,  groove  d'  connects  V  and  c,  and  b 
is  uncovered.  This  construction  prevents  waste  of  steam  if  the 
valve  piston  becomes  worn  in  its  cylinder,  since  live  steam  is  con- 
ducted  to  that  cylinder  only  during  the  moment  of  moving  the 
piston.  The  stroke  of  the  pump  can  be  easily  regulated  and  the 
action  is  noiseless. 

A  valve  with  a  peculiar  cut-off  action  is  used  on  the  Blake 
pump.  In  this,  as  it  stands  in  Fig.  54,  steam  is  entering  the  head 
end  of  the  cylinder  through  the  ports  E  and  II,  and  is  exhausting 
from  the  crank  end  through  ports  II',  E',  K  and  M.  As  the  main 
piston  A  nears  the  crank  end  of  the  stroke,  the  valve  C  is  moved 
to  the  left  by  a  system  of  levers  similar  to  those  on  the  Deane 
pump,  which  strike  tappets  on  the  rod  P.  When  this  happens  the 
lug  S  on  the  valve  C  covers  the  auxiliary  steam  port  N,  and  S'  un- 
covers  the  auxiliary  steam  port  N'  (see  plan  view),  while  the 
auxiliary  exhaust  port  Z  is  disconnected  from  X'  and  connected 
to  X,  thus  allowing  steam  to  exhaust  from  the  piston  chamber  at 
B'  and  flow  into  that  at  B.  The  main  valve  D  will  bo  carried  to 
the  right  by  the  supplemental  piston  and  will  connect  port  E  to  K, 
leaving  E'  uncovered  for  the  entrance  of  live  steam,  and  the  main 
piston  will  be  forced  towards  the  head  end.  It  is  not  necessary  to 
provide  for  positive  mechanical  driving  of  the  main  valve,  as  live 
steam  can  always  enter  one  end  or  the  other  of  both  main  and 
supplemental  cylinders.  The  supplemental  piston  is  fitted  with 
rings  so  that  it  will  take  up  its  own  wear,  and  prevent  leakage  into 
the  exhaust,  while  the  motion  is  such  that  the  main  valve  haa  a 
slight  lead  on  the  main  piston,  thus  admitting  live  steam  to 


327 


STEAM  PUMPS 


cushion  the  latter  at  the  end  of  its  stroke  and  prevent  slamming. 
Also,  in  case  the  main  valve  sticks,  the  valve  C  moves  far  enough 
to  admit  sufficient  steam  past  the  end  of  the  main  valve  for  the 
cushioning  effect.  The  supplemental  piston  cushions  on  the  steam 
caught  as  it  passes  by  the  end  of  the  port  X  or  X'. 


Fig.  54. 


The  Davidson  pump,  Fig.  55,  has  but  one  valve,  operated  by 
an  auxiliary  piston.  The  admission  of  steam  to  the  ends  of  this 
piston  is  accomplished  by  the  oscillating  motion  of  the  main 
valve  itself.  This  motion  is  caused  by  a  pin  turned  by  a  cam 
and  oscillating  lever  driven  from  the  pump  rod.  In  the  position 
shown,  3team  is  being  admitted  to  the  crank  end  ind  exhausted 


STEAM  PUMPS 


69 


from  the  head  end;  consequently  tlio  piston  is  moving  towards  the 
right.  As  it  nears  the  end  of  the  stroke,  the  cam  C  will  rotate 
the  pin  D  and  place  valve  A  in  position  to  connect  the  port  E' 
with  the  exhaust  chamber  while  opening  E  to  live  steam  as  seen 


.. 


in  the  end  view.  The  pin  D  will  then  be  driven  towards  the  left, 
carrying  with  it  the  valve  A.  Porte  E'  and  F  will  bo  closed  so 
that  the  niain  piston  will  be  cushioned  on  the  steam  remaining  in 
the  cylinder. 


329 


70 


STEAM  PUMPS 


The  movement  of  valve  A  to  this  central  position  opens  E'  to 
exhaust  and  E  to  live  steam,  and  the  piston  B  B',  carrying  with  it 
valve  A,  is  forced  to  the  left,  opening  port  F  to  exhaust  and  F'  to 
live  steam,  and  allowing  the  main  piston  to  move  towards  the  left 
When  valve  A  is  in  a  position  to  cover  both  ports  F  and  F',  either 
E  is  open  to  steam  and  E'  to  exhaust  or  vice  versa,  consequently 
the  pump  is  always  ready  to  start  as  soon  as  steam  is  turned  on. 

Various  other  forms  of  steam  end  have  been  used  by  differ- 
ent makers,  but  they  work  on  practically  the  same  principles  as 
those  described,  being  different  only  in  details. 

The  duplex  pump,  as  already  explained,  has  two  sets  of  cylin- 
ders side  by  side.  The  steam  valve  on  one  side  is  moved  by 


means  of  a  valve  rod  and  lever  connected  to  the  piston  rod  on  the 
other  side,  so  that  one  side  starts  when  the  other  has  reached 
about  three-quarters  stroke.  The  steam  valves  are  usually  of  the 
D  form,  having  separate  ports  for  admission  and  exhaust  at  each 
end  as  seen  in  Fig.  50.  In  this  figure,  valve  B  is  moved  by  rod 
C  and  bell-crank  lever  D,  the  hidden  end  of  which  is  driven  from 
the  farther  piston  rod  by  a  device  like  II,  while  the  farther  valve 
is  driven  by  the  rocker-arm  lever  G  F  E.  The  double  ports  are 
used  so  that  the  piston  may  run  over  the  exhaust  port  and  close 
it  before  reaching  the  end  of  the  stroke,  thus  getting  a  steam 
cushion,  and  yet  live  steam  may  have  a  chance  to  enter  behind  the 
piston  even  if  it  stops  quite  at  the  end  of  its  possible  motion.  In 
large  sizes  (particularly  in  fire  pumps)  a  cushion  valve  is  placed 


330 


I 

w  >•. 

S^  S 


1M 


£  &S 

*«* 

gg 

X 

H 

I 

^ 


PUMPS  71 

in  a  passage  connecting  che  steam  and  exhaust  ports,  so  that  the 
amount  of  by-pass  oper  ng  between  them  may  be  adjusted,  there- 
by  regulating  the  cushioning  to  any  desired  amount. 

In  order  to  secure  the  rest  period  at  the  end  of  each  stroke, 
which  is  needed  for  quiet  running  and  small  slip,  it  is  usual  to 
introduce  a  lost-motion  device  in  the  valve-driving  mechanism. 
In  Fig.  5G  this  is  the  nut  A, 
which  has  a  thickness  less  than 
the  space  between  the  lugs  on 
the  valve,  thus  preventing  the 
valve  from  being  moved  until 
the  nut  has  traveled  some  dis-  ' lg<  57< 

tance.  In  larger  sizes  it  is  more  common  to  use  a  single  lug  on 
the  valve;  the  rod  passes  through  this  and  the  lost  motion  is  pro- 
vided for  by  adjusting  nuts  held  fast  by  jam  nuts,  so  that  the  valve 
lug  will  have  play  between  them  as  seen  in  Fig.  57.  For  very 
large  pumps  and  pumping  engines,  lost-motion  links  are  usually 
placed  in  the  end  of  the  valve  rod,  as  seen  in  Fig.  58;  this  arrange- 
ment has  the  advantage  that  the  amount  of  lost  motion  can  be 
adjusted  without  removing  the  steam-chest  cover,  or  even,  if 
desired,  while  the  pump  is  in  motion.  It  is,  of  course,  somewhat 
more  expensive  to  construct  than  the  jam  nuts  shown  in  Fig.  57, 
hence  is  not  often  used  for  small  pumps. 

The  amount  of  lost  motion  needed  for  any  style  of  pump  can 
be  determined  only  by  trial,  but 
once  fixed  will  bo  the  same  for  all 
pumps  of  a  given  style  and  size. 
For  pumps  up  to  10-inch  stroke, 
£  to  |  inch  is  usually  allowed ;  for  larger  sizes  the  requirements 
call  for  J  to  1  inch. 

Compound  Pumps.  The  simple  steam  pump  must  from  the 
nature  of  its  action  take  steam  full  stroke,  hence  has  no  possi- 
bility of  using  any  of  the  expansive  energy  in  the  steam.  In 
order  to  overcome  this  difficulty  large  pumps  are  often  com- 
pounded, and  usually  with  cylinders  arranged  tandem,  as  in  Fig. 
59,  or  with  the  smaller  cylinder  outside,  as  the  designer  may 
"boose.  Steam  from  the  boiler  enters  the  high-pressure  steam- 


STEAM  PUMPS 


chest  in  the  usual  way;  it  then  passes  to  the  high-pressure 
cylinder;  from  there  k  exhausts  through  the  side-pipe,  seen  at  the 
back  of  the  steam-chests  in  Fig.  59,  to  the  low-pressure  steam, 
chest;  thence  passes  into  the  low-pressure  cylinder  and  from  it  to 
the  exhaust  pipe.  Unless  a  boiler  pressure  of  more  than  80 
pounds  is  used,  it  is  not  advantageous  to  compound  a  pump  run 
non-condensing,  as  the  saving  in  steam  will  not  pay  for  the 
increased  cost.  If  a  condenser  is  used,  compounding  may  be 
introduced  with  profit  for  pressures  as  low  as  50  pounds;  but  the 
added  complication  of  condenser  and  many  cylinders  is  inad vis- 


Fig.  59, 


able  for  pumps  with  low-pressure  cylinders  smaller  than  about 
18X24  inches. 

Compound  pumps  are  used  either  single  as  in  Fig.  CO  with 
an  auxiliary  valve  and  valve  piston,  or  duplex  with  the  valves 
driven  by  the  method  described  for  duplex  pumps.  As  the 
pistons  are  on  the  same  rod,  the  valves  must  move  at  the  same 
instant,  and  are  usually  mechanically  connected  and  driven  by  the 
same  valve  piston  or  lever,  as  the  case  may  be.  The  duplex  com- 
pound is  more  often  used  than  the  single,  and  it  is  considered 
better  practice  to  use  a  duplex  compound  with  small  cylinders 
than  to  use  a  single  compound  with  larger  ones,  as  the  difference 
in  cost  will  be  more  than  balanced  by  the  steadiness  of  running 


STEAM  PUMPS 


73 


333 


74  STEAM  PUMPS 


The  high-pressure  cylinder  takes  steam  full  stroke  so  that 
there  is  no  expansion  in  it;  at  the  opening  of  the  high-pressure 
exhaust  the  pressure  drops  until  it  is  equalized  in  the  low-pressure 
steam-chest,  side-pipe,  high-pressure  cylinder,  and  the  clear- 
ance space  of  the  low-pressure  cylinder,  the  admission  to  which 
opens  at  the  sume  instant  as  the  exhaust  from  the  high-pressure. 
On  the  return  stroke  of  the  pump,  the  steam  expands  in  passing 
from  the  high-pressure  cylinder  to  the  low-pressure,  the  action 
being  as  indicated  in  the  diagram,  Fig.  61,  and  the  nominal  ratio 
of  expansion  between  2  and  3.  In  the  diagram  it  is  taken  as  2.25, 
vertical  distances  being  laid  off  to  represent  pressures  and  hori- 
zontal to  represent  volumes.  The  pressure  in  the  passages  be- 
teen  cylinders  is  a  variable,  but  is  taken  as  the  value  at  the 
beginning  of  the  low-pressure  stroke.  The  back  pressure  in  the 
low-pressure  cylinder  will  be  about  2  pounds  above  that  at  the 
outlet  of  the  exhaust  pipe,  or  17  pounds  for  a  non-condensing 
pump  und  4  pounds  for  one  run  condensing. 

The  action  illustrated  in  Fig.  61  is  as  follows  :  Assume  that 
we  are  dealing  with  a  pump  whose  high-pressure  cylinder  A  is  16 
inches  in  diameter  by  18  inches  stroke,  and  with  clearance  C  8 
per  cent  of  the  piston  displacement ;  and  whose  low-pressure 
cylinder  B  is  24  inches  in  diameter,  the  stroke  being  of  course 
the  same  as  for  the  high-pressure,  and  the  clearance  C  8  per  cent 
of  the  low-pressure  piston  displacement.  The  intermediate  space 
between  cylinders,  side-pipe  and  low-pressure  steam -chest  will  be, 
in  practice,  about  0.35  the  piston  displacement  of  the  high-pressure 
cylinder.  Assume  that  the  initial  pressure  is  85  pounds  gauge  or 
100  pounds  absolute  and  the  back  pressure  in  the  low-pressure 
cylinder  4  pounds  absolute.  The  line  a  b  will  represent  the  action 
during  admission  to  the  head  end  of  the  high-pressure  cylinder, 
steam  being  taken  at  full  pressure  for  the  entire  stroke.  If  we 
assume  the  volume  of  the  piston  displacement  as  1,  there  will  be 
1.08  volumes  of  steam  in  the  high-pressure  cylinder  and  clearance. 
At  the  end  of  the  stroke,  the  exhaust  through  the  side-pipe  into 
the  low-pressure  cylinder  will  be  opened  and  the  pressure  will  fall, 
the  amount  of  the  instantaneous  drop  depending  on  the  pressure 
in  the  low-pressure  steam-chest  at  the  time  the  high-pressure  ex- 
haust  opens.  We  shall  see  that  this  will  be  about  40  pounds,  a 


334 


STEAM  PUMPS 


75 


value  which  can  be  safely  assumed  as  a  working  basis.  When  the 
high-pressure  exhaust  opens,  the  admission  to  the  low-pressure 
cylinder  also  opens,  and  the  pressure  will  drop  according  to  Boyle's 
law,  so  that  it  is  equalized  in  the  three  compartments. 

The  volume  of    the  low-pressure  cylinder  will  be  1.52  X  1 
=  2.25,  and  of  its  clearance  .08  X  2.25  =  0.18  volumes.     Then 
the  pressure  after  drop  and  equalization  is  found  thus: 
1.08X100  =  108.00      109W9 

.35X40  =   14.00      1"""-'"'==762 
_J.8X4     = .72          LG1 

1.61  122.72 


100 


-pr 


The  pressure  after  equalization,  76.2  pounds,  is  found  by 
multiplying  each  volume  by  the  pressure  existing  within  it  and 
dividing  the  sum  of  the  products  by  the  sura  of  the  volumes. 

As  the  pistons  return,  the  volume  in  the  high-pressure  cylin- 
der decreases,  that  in  the  intermediate  passages  remains  constant, 
and  that  in  the  low-pressure  cylinder  increases.  The  result  will 
be  an  expansion  according  to  the  hyperbolic  law  so  that  the  line 
showing  the  back  pressure  on  the  high-pressure  piston,  and  that 
showing  forward  pressure  on  the  low-pressure  piston,  will  indicate 
the  same  pressure  at  each  instant  of  the  stroke,  though  the  low* 


335 


76  STEAM  PUMPS 


pressure  volume  will  be  2.25  times  the  high  pressure.  At  ^ 
stroke  the  total  volume  will  be 

.08  +  .75  -f  .35  +  .18  +  (J  X  2.25)  =  1.92  volumes, 
and  the  pressure  122.72  -=-  1.92  =  64  pounds. 

Similarly  at  i  stroke  the  pressure  will  be  55     pounds, 
at  |     "         "         "  "     "  48.3  pounds, 

at  full     "         "         «  "     "  42.9  pounds, 

and  so  on  for  other  points  so  that  the  whole  expansion  curve  may 
be  determined.  In  practice  there  will  be  a  difference  of  about  one 
pound  between  the  back  pressure  in  the  small  cylinder  and  the 
forward  pressure  in  the  large  one,  due  to  the  friction  of  the  steam 
in  ports  and  side-pipe.  On  the  next  stroke,  the  head  end  of  the 
high-pressure  cylinder  will  take  in  a  fresh  charge  of  steam  while 
the  crank  end  of  the  low-pressure  will  exhaust  its  steam  into  the 
condenser.  The  crank  end  of  the  small  cylinder  and  the  head  end 
of  the  large  one  act  together  in  the  same  manner  as  described  above, 
so  that  the  pump  is  double-acting. 

We  are  indebted  to  a  paper  on  "Power  of  Compound  Pumping 
Engines,"  by  John  W.  Hill,  published  in  Engineering  News,  for 
the  proportions  given  in  Table  VIII: 

TABLE  VIII. 

Ratio  diameter  1.  p.  cylinder 

to       h.  p.        " 1.50 1.60 2.00 

High-pressure  cylinder  volume  taken  as  1.00 1.00   1.00 

High-pressure  clearance  volume 063—     -   .063 .06 

Intermediate  space  volume 339 .339 1.12 

Low-pressure  cylinder  volume 2.25 2.56  4.00 

"  "        clearance     "       112 •  .128 .204 

No.  expansions  intermediate  chamber. .  1.319 1.439 2.250 

No.  expansions  1.  p.  cylinder  .  •. 1.825 2.020 2.258 

No.  expansions,  total 2.400 2.907 5.081 

Ratio  Mean  Effective  pressure  to  (Initial 

pressure  minus  back  pressure) 0.729 —  0.682 0.466 

Setting  the  valves  on  a  pump  is  for  the  most  part  a  simple 
operation,  and  requires  only  that  the  valves  shall  be  adjusted, 
usually  by  trial,  until  the  pump  makes  the  longest  stroke  possible 
without  striking  the  heads,  and  reverses  evenly  at  the  ends  of  the 
stroke. 

The  fly-wheel  pump  is  adjusted  by  moving  the  eccentric  on 


STEAM  PUMPS  77 


the  shaft  and  the  valve  on  its  stem  until  steady  running  is  secured, 
the  same  as  for  any  slide-valve  engine.  The  Knowles  pump  has 
the  stroke  lengthened  by  lowering  the  roll  E,  Fig.  50,  and  short- 
ened  by  raising  it;  equalization  of  reversal  is  effected  by  lengthen- 
ing  or  shortening  the' link  L  as  may  be  required. 

Adjustment  of  the  Deane  pump  is  made  entirely  by  moving 
the  tappets  on  the  valve  rod;  the  block  A  should  be  clamped  to 
the  piston  rod  in  such  position  that  when  the  piston  is  at  mid- 
stroke  the  link  B  will  be  vertical.  With  the  valve  in  mid-position 
the  tappets  should  be  placed  so  that  they  are  equidistant  from 
each  end  of  the  sliding  collar,  and  then  adjusted  by  trial  until 
the  working  is  satisfactory.  If  the  piston  strikes  at  either  end, 
move  the  tappet  at  that  end  towards  the  collar;  if  reversal  comes 
too  soon  at  one  end,  move  the  tappet  away  from  the  sleeve  at  that 
end. 

For  the  Dean  Bros.'  purnp  the  same  directions  apply  as  to  the 
Deane,  but  the  stroke  may  be  changed  by  moving  the  bolt  B, 
Fig.  53,  in  its  slot  without  changing  the  tappets. 

The  adjustment  of  the  Blake  valve  is  also  the  same  as  that 
for  the  Dean  Bros.',  but  the  tappets  on  the  valve  rod  should  be  so 
set  that  the  valve  will  have  a  little  lead  and  open  before  the  main 
piston  reaches  the  end  of  its  stroke.  It  has  this  lead  by  virtue  of 
the  action  previously  explained  unless  it  is  set  to  be  very  late  in 
action. 

In  the  Davidson  pump,  Fig.  55,  the  valve  is  adjusted  for 
length  of  stroke  by  moving  the  bolt  in  the  slotted  end  of  the  oscil- 
lating arm;  shortening  the  leverage  shortens  the  stroke  and  vice 
versa.  To  equalize  the  reversal,  the  sleeve  which  is  clamped  to 
the  piston  rod  may  be  shifted  towards  the  end  at  which  it  is 
desired  to  quicken  the  reversal,  or  a  slight  adjustment  may  be 
made  at  the  point  where  the  oscillating  lever  is  made  fast  to  the 
rock-shaft  which  drives  the  cam  C. 

For  a  single  compound  pump  the  valves  are  adjusted  in  the 
same  way  as  for  a  simple  pump  of  the  same  make.  There  is  an 
adjustment  in  the  connection  between  high-  and  low-  pressure 
valves,  and  this  must  be  set,  with  the  steam-chest  covers  off.  so 
that  the  main  valves  open  at  the  same  time. 

All  the  valves  of  the  duplex  pump  are  set  square  so  that,  with 


337 


78 


STEAM  PUMPS 


Fig.  62. 
FULTON  CORLISS  CYLINDER. 


.GOVERNOR    KNOCK-OFF   ROD 
/AND  HEAD 


KNOCK-OFF  CAM  LEVER 


SAFETY    CAM 
STEAM 


DASH  POT  ROD  I 
AND  HEAD 


Fie.  63. 


STEAM  PUMPS 


79 


both  pistons  at  the  middle  of  the  stroke,  the  valves  will  be  in  mid . 
position,  the  rocker-arm  levers  will  be  vertical  and  the  lost  motion 
will  have  equal  play  at  each  end.  The  amount  of  lost  motion  needed, 
where  it  is  adjustable,  can  be  determined  only  by  trial,  but  gen- 
erally should  be  as  great  as  possible  without  having  the  pistons 
strike  the  heads.  This  will  give  a  long  stroke. 

For  the  large  pumping  engines  used  in  city  water-works,  the 
steam  ends  are  designed  the  same  as  for  any  steam  engine;  and  fly- 
wheels, main  shafts  and  eccentrics  are  provided  for  steadying  the 
motion,  allowing  of  expansive  working  and  operating  the  valves. 
For  such  engines  the  Corliss  valves  and  valve  motion  have  been 
most  commonly  used  in  the  United  States. 

The  arrangement 
of  the  motion  and  the 
action  of  the  valves   is 
shown  in  Fig.  62.    The  ' 
wrist  plate  is  moved  by 
the  eccentric  through  a 
reach -rod,  rock- shaft  and 
eccentric  rod,  and  from 
it   links  run   to  cranks 
which  turn  the  rotating 
valves  in   their  seats. 
The  exhaust  valves  are 
positively   driven,  but 
the  admission  valves  are  so  arranged  as  to  be  disconnected  from 
the  control  of  the  link  at  some  point  in  the  stroke  (depending 
on  the  position  of  the  governor)  by  a  trip  motion,  one  form  of 
which  is  shown  in  Fig.  63. 

Another  device  used  to  allow  of  expansive  working  of  steam 
in  large  pumps  is  the  hydraulic  compensator,  Fig.  64.  The 
steam  must  work  against  the  pressure  of  the  pistons  up  to  half 
stroke,  and  is  assisted  by  it  beyond  that  point,  so  that  cut-off  may 
take  place  at  half  stroke,  or  later,  and  the  energy  of  expansion  be 
used  beyond  that  point,  With  this  device,  there  is  no  shaft  or 
eccentric,  and  valves  similar  to  those  described  for  duplex  pumpa 
are  used. 


Fig.  64. 


80  STEAM  PUMPS 


ERECTION  AND  PIPING. 

The  location  of  a  pump  should  be  chosen  with  two  principal 
objects  in  view:  To  have  the  pump  itself  convenient  for  running, 
and  accessible  for  repairs  or  adjustment;  and  to  keep  the  piping 
as  short  and  direct  as  possible.  For  a  pump  to  which  the  liquid 
is  raised  by  suction  there  is  the  limitation  that  it  must  not  be  placed 
more  than  25  feet,  and  should  not  be  more  than  20  feet,  above  the 
source  of  supply;  but  aside  from  this,  a  matter  of  first  import- 
ance is  to  have  the  machine  where  it  will  naturally  be  kept  in  good 
condition.  Too  often  a  pump  is  placed  in  a  dark  corner  where  it 
is  never  seen,  seldom  visited,  and  always  neglected;  it  soon  becomes 
dirty  and  leaky,  decreasing  its  efficiency  and  shortening  its  life. 
The  second  point  with  respect  to  piping  is  often  controlled  by  the 
layout  of  other  apparatus  quite  as  much  as  by  the  position  of  the 
pump  itself;  yet  by  careful  study  of  the  conditions  it  is  often  pos- 
sible to  find  one  place  better  than  others  for  the  pump.  It  is  of 
more  importance  to  avoid  bends  and  elbows  in  water  piping 
than  in  that  for  steam,  because  steam  makes  sharp  turns  with 
less  friction  loss  than  does  water.  If  hot  water  is  to  be  handled, 
the  water  should  flow  to  the  pump  by  gravity  or  under  pressure. 
Otherwise  the  water  will  turn  into  vapor  under  the  suction  force 
and  the  pump  will  draw  in  either  vapor  alone  or  a  mixture  of 
vapor  and  water. 

It  is  well  to  place  a  boiler  feed  pump  in  such  a  position  that 
the  gauge  glass  can  be  seen  when  standing  at  the  pump,  but  this 
is  not  absolutely  essential,  and  should  be  sacrificed  if  any  gain  in 
arrangement  of  piping  or  convenience  of  attendance  can  be  secured 
thereby.  If  a  condenser  air-pump  is  so  placed  that  the  water 
from  the  condenser  flows  to  it  by  gravity,  it  is  possible  to  maintain 
a  better  vacuum  in  the  condenser. 

Wherever  the  pump  may  be  located,  a  substantial  foundation 
should  be  provided  if  the  pump  is  of  large  size,  especially  if  it  is 
to  be  run  at  high  speed.  It  is  often  sufficient  to  fasten  a  small 
pump  to  the  floor  or  to  heavy  brackets  secured  to  a  wall,  but  a 
pump  larger  than  a  4  X  6  should  have  a  separate  foundation.  In 
designing  the  foundation,  remember  that  the  object  is  not  so  much 
to  hold  the  pump  up  as  to  hold  it  down,  to  keep  it  from  vibrating. 


340 


STEAM  PUMPS  81 


It  is,  therefore,  better  to  have  a  foundation  deep  and  narrow  than 
broad  and  ehallow,  unless  the  pump  is  large  and  the  soil  very 


The  pump  should  be  well  bolted  to  the  foundations  in  order 
to  prevent  vibration,  as  such  movement  not  only  is  communicated 
to  the  pipe  and  thence  to  the  building,  but  tends  to  loosen  the 
joints  in  the  piping  and  the  pump  itself.  Absolute  rigidity  on  the 
foundations  should  be  secured  at  any  cost. 

The  material  may  be  stone,  brick,  or  concrete,  preferably  the 
last.  Stone  is  expensive  and  difficult  to  work;  brick  is  liable, 
unless  carefully  laid  with  cement  mortar,  to  be  loose  and  lack 
compactness;  while  concrete  is  easily  put  down,  is  inexpensive  and 
has  all  the  solidity  of  stone.  It  should  be  made  of  good  cement 
mortar,  two  parts  sand  to  one  Portland  cement,  mixed  with 
broken  stone-  not  over  2  inches  in  longest  diameter,  in  equal 
parts  of  stone  and  mortar,  The  concrete  should  be  well  com- 
pacted into  a  mould  the  shape  of  the  foundation,  the  bolts  being 
built  in  with  plate-iron  washers  on  the  heads;  the  concrete  should 
be  deposited  in  layers  about  6  inches  deep  and  well  rammed,  a 
second  layer  being  added  beforo  the  upper  surface  has  hardened. 
This  process  is  repeated  until  the  foundation  is  completed.  It  will 
generally  be  sufficient  to  finish  the  top  with  a  surface  of  cement 
mortar  carefully  leveled  and  allowed  to  harden  before  setting  the 
pump,  but  sometimes  a  cast-iron  base-plate  is  used,  and  this  gives 
f*  somewhat  neater  appearance. 

As  previously  stated,  the  piping  should  be  as  3hort  und 
direct  as  possible.  In  large  work,  the  water  pipe  should  have 
long-bend  elbows  and  tees,  and  gate  valves  should  be  used  to 
reduce  the  friction.  Each  pipe  should  be  pitched  throughout  its 
length  to  one  point  so  that  it  may  be  drained  to  avoid  freezing;  a 
drain-cock  should  be  placed  at  the  lowest  point  to  remove  the 
water.  For  water  piping,  it  is  well  to  use  galvanized  or  brass 
pipe  to  avoid  pitting  or  corrosion.  Covering  the  pipes  which 
carry  cold  water  will  prevent  sweating  and  the  consequent  unpleas- 
ant dripping. 

If  the  plant  is  one  where  a  shut-down  would  be  serious,  a 
duplicate  system  should  be  installed,  pump,  piping  and  all;  for 
any  plant  it  ia  well  to  provide  an  injector  as  relay,  in  case  the 


341 


82  STEAM  PUMPS 

boiler  feed-pump  will  not  work.  In  some  cases  duplicate  piping 
is  installed,  but  this  seems  hardly  necessary,  as  piping  is  not 
likely  to  get  out  of  order  if  well  taken  care  of. 

Wherever  a  long  column  of  water  is  to  be  moved  in  either 
suction  or  delivery  pipes,  it  is  well  to  place  a  check  valve  near  the 
lower  end  of  the  column  to  resist  any  tendency  of  the  water  to 
back  up  when  the  pump  reverses  or  shuts  down.  In  the  suction 
system  this  valve  would  be  placed  on  the  inlet  end  of  the  suction 
pipe  and  is  known  as  a  foot  valve,  Fig.  65.  For  the  delivery 


Fig.  65. 

pipe,  it  is  well  to  use  a  check  valve  near  the  outlet  from  the  pump 
and  another  near  the  end  of  the  pipe,  especially  if  pumping  against 
high  pressure.  The  check  valves  may  be  of  either  flap  or  disc 
type,  but  if  of  the  latter  they  should  have  ample  area  so  that  the 
double  turn  made  by  the  current  of  water  will  not  cause  great  loss 
of  head.  The  flap  valve  is  shown  in  Fig.  66  and  the  disc  form  in 
Fig.  67. 

For  all  pumps  which  are  to  handle  water  from  ponds,  rivers 
or  other  sources  where  sticks,  leaves,  or  any 
form  of  rubbish  is  likely  to  collect,  a  strainer 
as  shown  in  Fig.  65  should  be  placed  on  the 
end  of  the  inlet  pipe.  The  combined  area  of 
the  openings  into  the  strainer  should  be  3  to 
4  times  the  area  of  the  pipe.  As  rubbish 
quickly  collects  on  a  horizontal  strainer,  the 
surface  should  be  either  slanting  or  vertical, 
Fig.  66.  an(j  ghouj^  ke  so  designed  that  the  screen 

may  be  easily  cleansed.  The  straining  surface  should  be  fine 
or  coarse  in  mesh  according  to  the  material  to  be  screened,  and 
made  of  woven  wire  or  perforated  metal  as  may  be  most  con- 


342 


STEAM  PUMPS 


83 


venient.  Often  the  foot  valve  and  strainer  are  combined  into  a 
single  piece.  If  the  lower  end  of  the  suction  pipe  is  not  accessible 
for  cleaning,  and  if  the  debris  is  of  such  nature  that  it  is  likely 
to  clog  the  openings,  it  will  be  better  to  use  a  design  given  by 
Barr  (see  Fig.  68)  placed  near  the 
pump. 

The  sizes  ol  pipe  needed  for 
the  suction  and  delivery  are  deter, 
rained  by  the  pump  maker  and  the 
pipes  should  never  be  made  smaller 
than  these;  if  the  runs  are  long,  the 
pipes  may  well  be  made  larger. 

The  velocity  allowable  is,  of 
course,  the  point  which  determines 
these  diameters.  For  the  suction, 
this  ia  usually  taken  at  200  feet  per 


Fig.  67. 


minute  or  less  ;   for  the  delivery  pipe  it  may  be  400  feet  per 

minute  or  less. 

The  suction  pipe  should  be  of  the  same  size  throughout  in 

order  to  avoid  eddies  and  changes  of  velocity.     Where  the  pipe  is 

larger  than  the  pump  connection,  the  reduction  should  be  made  by 

a  conical  pipe  with  an  easy  taper,  placed  next  the  pump.     The 

greatest  care  should  be 
taken  to  see  that  all  joints 
in  the  suction  system  are 
absolutely  tight,  as  even  a 
small  leak  greatly  reduces 
the  capacity  and  efficiency. 
The  diameters  of  pipe 
suitable  for  direct -act  ing 
pumps  are  given  in  Table 
IX,  the  suction  velocity 

being  allowed  at  150,  and  delivering  velocity  at  300  feet  per  minute. 
The  loss  in  head  depends  on  the  length  of  the  piping  and  the 

rate  of  flow  of  the  water.     Table  X  gives  the  loss  in  pounds  pres. 

sure  per  100  feet  of  pipe  for  various  rates  of  discharge  and  sizes 

of  pipe  as  stated  by  G.  A.  Ellis. 

The  losa  of  head  from  elbows  and  valves  depeadc  also  on  the 


Fig.  68. 


343 


84 


STEAM  PUMPS 


TABLE  IX. 

SIZES  OP  SUCTION  AND  DELIVERY  PIPES. 


Diameter  Suction  Pipe. 

Diameter  Delivery  Pipe. 

Diameter 
Water  Cylinder. 

Single 
Pump. 

Duplex 
Pump. 

Single 
Pump. 

Duplex 
Pump. 

4  inches 

2^  inches 

3)^  inches 

1^  inches 

2^  inches 

5        " 

3 

4 

2          " 

3 

6        " 

3^ 

5 

2^       || 

3</2 

7        " 

W 

G 

4 

8 

5 

7 

3#       " 

4^ 

9 

6 

8 

4^       " 

6 

10 

6 

o 

4^       " 

6 

12 

7 

10 

5          " 

7 

14 

9 

12 

6 

8 

1C 

10 

14 

7 

9 

18 

12 

16 

9          " 

12 

20 

12 

17 

9 

12 

Suction  velocity,  150  feet  per  minute. 
Delivery  velocity,  300  feet  per  minute. 
Piston  speed,  100  feet  per  minute. 

rate  of  flow,  and  is  most  conveniently  referred   to  the  length  of 
pipe  which  would  result  in  the  same  loss. 

The  resistance  to  flow  of  water  in  pipes  due  to  bends,  elbows, 
tees,  etc.,  is  stated  by  Foster  in  his  "  Electrical  Engineer's  Pocket 
Book,"  to  be  expressed  by  the  equation: 

P-F 


in  which  P  is  the  loss  in  pressure  in  pounds  per  square  inch, 
v  the  velocity  of  flow  in  feet  per  second,  and  F  the  coefficient 
of  friction,  \vhich  varies  with  the  angle  of  the  bend  according  to 
the  following  table: 

Angle.     20°          45°         60°          90°          120°        135° 
F         .020       .079       .158        .426        .806        .940 

A  globe  valve  will  produce  the  same  loss  of  head  as  two  90- 
degree  bends,  and  a  gate  valve  a  loss  equal  to  that  from  a  45  -degree 
bend. 

If  water  is  known  to  contain  lime  or  magnesia,  it  is  certain 
that  pipes  will  fill  up  more  or  less  from  the  deposit  of  scale,  and 
allowance  should  be  made  for  this  in  the  first  place  by  using  extra 
large  pipe. 


344 


STEAM  PUMPS 


85 


In  choosing  the  size  of  steam  pipe  the  same  general  principle 
applies;  the  exhaust  pipe,  like  the  suction,  should  be  short,  direct, 
and  of  ample  cross-section.  A  velocity  of  6,000  feet  per  minute 
is  allowable  in  the  steam  pipe  and  4,000  in  the  exhaust. 

Care  should  be  taken  to  have  all  piping  which  carries  steam 
pitched  away  from  the  pump  to  avoid  the  collection  of  the  water 
of  condensation  in  the  steam  cylinder,  and  drips  should  be  pro- 
vided wherever  there  is  any  chance  for  water  to  collect. 

The  use  of  air  chambers  has  already  been  discussed.  They 
are  usually  a  good  investment  if  high  speed  or  long  pipe  runs  are 
to  be  used.  The  gain  in  durability  and  saving  of  repairs  to  the 
pump  and  piping  system  will  more  than  pay  the  interest  on 
the  small  cost  of  ample  air  chambers. 
TABLE  X. 

FRICTION  OP  WATER  IN  PIPES. 

Friction  loss,  in  pounds  pressure  per  square  inch,  for  each  100  feet  of 
length  of  different  sizes  of  clean  iron  pipe  discharging  given  quantities  of 
water  per  minute.  G.  A  ELLIS,  C.  E. 


SIZES  OF  PIPES — INSIDE  DIAMETER 


Minute 

5 

10 
15 
20 

25 
30 
35 
40 
45 
50 
75 
100 
125 
150 
175 
200 
250 
300 
350 
400 
450 
500 
750 
1000 
1250 
1500 
1750 
2000 
22.50 
2500 
3000 
.3500 
4000 
4500 
5000 

Comparative 
Discharging 
Power  of  Hi|.es 

Kin. 

lin. 

1% 
in. 

1 

in. 

2  in. 

V/2 

in. 

Sin. 

4  in. 

Gin. 

8in. 

10 
in. 

12 
in. 

14 

16 

18 

in. 

3.3 
13.0 
28.7 
50.4 
78.0 

0.84 
3.16 
6.98 
12.3 
19.0 
27.5 
37.0 
48.0 

0.31 

1.05 
2.38 
4.07 
6.40 
9.15 
12.4 
16.1 
20.2 
24.9 
56.1 

0.12 
0.47 

0.97 
1.66 
2.62 
3.75 
5.05 
6.52 
8.15 
10.0 
22.4 
39.0 

0.05 
0  1° 

0.30 
0.42 
0.51 
0.91 

l.'Jli 
1.60 
2.00 
2.41 
5.32 
9.46 
14.9 

0.11 
0.15 
0.21 

0.33 
0.45 
0.52 
0.65 
0.81 
1.80 
3.20 
4.89 
7.0 
9.16 
12.47 
19.66 
28.06 

0.10 
0.11 
0  17 

0.22 
0.28 
0.35 
0.74 
1.31 
1.9! 
2.85 
£.S5 
5.02 
7.76 
11.2 
15.2 
19  5 

'0.09 
0.17 
0.33 
0.53 
0.0! 
1.00 
1  '"2 
l!x<i 
2.611 
3>>5 
4  73 



0.05 

0.10 

0.03 
0.01 
0.05 
0.06 
0.07 
0.09 
0.18 
0.32 
0.49 
0.70 
0.95 
1.23 

b.oi 

'0.02 

'b'.03 
0.04 
0.08 
0.13 
0.20 
0.29 
0.38 
0.49 
0.63 
0.77 
1.11 

498.S 

28.1 
37.5 

o.oii 

0.062 

b.i35 

0.234 

0.362 
0.515 

0>.i7 
0.910 

733.4 

6.009 
6!636 

o.oii 
0.123 
Y.iss 

1.267 

i.:;65 
0.472 
0.59.'! 
0.730 

1024. 

0.003 
0.626 
0.040 

b'.on 

0.107 
D.I  50 
0.204 
0.263 
0.883 
0.408 

1375. 

'.'.'.'.'. 

0.17 
0.26 
0.37 
0.50 
0.65 
O.S1 
0.96 

8.88 

'b'.07 
0.09 
0.12 
0.16 
0.20 
0.25 
0.53 
0.94 
1.46 
2.09 

.'5.0 
30.8 

6.01 
7.43 

9.88 

15.59 

?-& 

32. 

1 

1.75 

2.76 

5.66 

88.2 

181 

316.2 

345 


86  STEAM  PUMPS 


Care  should  be  taken,  however,  that  no  pockets  are  formed  in 
the  piping  where  air  may  collect,  as  the  air  cushion  thus  formed 
will  serve  no  useful  purpose,  but  will  reduce  both  the  capacity  and 
the  efficiency  of  the  pump.  The  suction  pipe  should  have  a  con- 
tinuous  rise  from  the  source  of  supply  up  to  the  pump;  and  if  an 
inverted  U  loop  must  be  formed  in  the  delivery  piping  it  should 
have  a  pet  cock  inserted  at  the  highest  point  so  that  whatever  air 
collects  may  escape. 

CARE. 

After  the  valves  of  a  pump  are  properly  adjusted,  the  three 
things  which  ordinarily  require  care  are:  The  lubrication,  the 
packing,  and  the  draining  of  cylinders.  If  these  matters  are  care- 
iuJ'ly  attended  to,  the  pump  will  cause  very  little  trouble. 

For  the  smaller  sizes  the  steam  end  is  generally  lubricated  by 
means  of  a  grease  cup,  which  is  filled  with  some  form  of  tallow 
compound.  As  the  heat  of  the  steam  melts  this  compound  grad- 
ually, it  flows  into  the  steam -chest  and  is  carried  by  the  steam  to 
tfie  cylinder.  For  larger  sizes,  a  regular  cylinder  oiler  is  used,  or 
sometimes  an  oil  pump  driven  by  a  lever  from  the  main  piston 
rod.  In  large  plants,  the  pumps  as  well  as  the  engines  a're  fed 
from  a  central  tank  into  which  the  oil  is  forced  under  pressure  by 
a  single  large  oil  pump,  and  whence  it  descends  by  gravity  to  the 
various  cylinders  and  passes  through  sight-feed  oilers. 

The  stuffing  box  on  the  steam  end  usually  gets  sufficient 
lubrication  from  the  cylinder,  and  the  one  on  the  water  end  gets 
water  enough  except  when  the  packing  is  set  up  hard;  then  a  little 
machine  oil  with  graphite  in  suspension  will  help. 

In  the  case  of  the  steam-cylinder  as  for  any  other  engine, 
the  less  oil  used,  so  long  as  the  piston  works  quietly,  the  better. 

Flake  graphite  put  into  cylinder  oil  usually  settles  to  the 
bottom  of  the  cup,  but  if  blown  into  the  steam  pipe  so  as  to  be 
carried  along  by  the  steam,  it  will  work  into  the  crevices  in  valves 
and  piston  rings  and  aid  materially  in  reducing  the  oil  required. 
Also  if  sifted  over  the  packing  when  filling  the  stuffing  boxes  it 
will  reduce  the  friction  considerably. 

For  the  bearings  of  valve  motions,  machine  oil  is,  of  course, 
used.  These  parts  need  the  same  care  as  any  other  machine 
bearings. 


346 


SSI 


I! 

5   a 

ll 

s5 

5  2 


STEAM  PUMPS  87 


The  packing  in  the  water  piston  wears  but  slowly;  neverthe- 
less it  should  be  regularly  inspected  to  make  sure  that  there  are 
no  leaks,  as  they  would  seriously  impair  the  economy  of  the  pump. 
Once  in  two  months  is  not  too  often  to  examine  the  water  pistons, 
and  oftener  should  be  the  rule  if  there  is  any  reason  to  suspect 
trouble.  In  repacking,  or  in  tightening  up  either  piston  or  stuf- 
fing boxes,  there  should  be  as  little  pressure  as  possible,  above  the 
limit  to  prevent  leakage. 

The  piston  ring  packing  of  the  steam  end  will  wear  for  years 
if  properly  adjusted  and  lubricated.  An  inspection  once  a  year 
18  sufficient  unless  suspicious  action  in  the  cylinder  seems  to  call 
for  an  investigation. 

The  stuffing  boxes  should  be  kept  tight,  but  not  screwed  up 
BO  as  to  bind.  It  pays  to  be  rather  generous  both  in  the  amount 
of  packing  used  in  a  stuffing  box  and  in  frequency  of  renewals  ; 
the  former  because  a  long  bearing  between  rod  and  packing  will 
keep  tight  with  less  pressure  than  a  short  one  4  the  latter  because 
old,  hardened  packing  requires,  a  heavy  pressure  to  force  it  to  a 
tight  joint,  and  "-results  in  ?a  large  amount  of  energy  wasted  in 
overcoming  friction.  For  stuffing  boxes,  any  good  square  packing 
will  answer,  but  the  one  on  the  water  end  is  better  filled  with 
some  form  having  a  rubber  compound  for  its  main  body,  while  that 
on  the  steam  end  works  better  with  a  flax  packing,  as  the  steam 
soon  kills  the  rubber.  Stuffing  boxes  should  be  refilled  as  often 
as  twice  a  year,  if  the  pump  is  in  constant  service. 

The  valves  in  the  steam  end  have  a  sliding  bearing,  and  will 
ordinarily  wear  to  a  true  and  tight  joint.  At  the  time  of  the 
yearly  inspection,  the  head  should  be  removed,  steam  turned  on, 
and  the  valve  wrorked  back  and  forth  by  hand  to  mako  sure  that 
no  steam  passes  into  the  cylinder  except  when  the  admission  valve 
is  properly  open.  If  the  valves  leak,  they  must  be  scraped  to  a 
bearing.  Usually  the  valve  face  is  scraped  accurately  by  using  a 
surface  plate,  and  the  seat  is  then  scraped  to  fit  the  valve. 

The  valves  in  the  water  end  may  be  reseated  by  grinding  the 
seats  and  faces  with  tools  made  for  the  purpose,  if  both  the  valves 
and  seats  are  of  metal.  If  the  valves  have  a  bearing  surface  of 
composition,  as  is  now  the  usual  praciice,  the  composition  disc  will 
wear  rather  than  the  seat,  and  the  disc  may  be  renewed  easily  and  at 


84* 


88  STEAM  POMPS 

slight  expense.  Some  makers  use  discs  of  soft  alloy  which  are 
more  durable  than  composition  and  also  have  its  advantages. 

In  discussing  the  subject  of  capacity,  the  matter  of  speed  was 
taken  up.  Manufacturers  conventionally  rate  their  pumps  at  100 
feet  per  minute,  but  this  is  not  a  good  basis,  and  sixty  double 
strokes  seem  to  be  more  logical  for  computation.  The  object  is 
to  reduce  slip  and  prevent  pounding;  hence,  if  special  devices  are 
used  for  opening  and  closing  the  water  valves  and  to  prevent 
slamming  at  the  end  of  the  stroke,  there  is  no  reason  why  a  speed 
may  not  be  used  approaching  that  of  power  engines.  The  slip 
occurs  almost  entirely  at  the  ends  of  the  stroke  and  during  the 
seating  of  the  valves,  so  that  it  ia  always  well  to  use  a  long  stroke 
ever  though  the  diameter  be  somewhat  small. 

If  mechanically  operated  valves  together  with  high  speed  are 
used,  ample  air  chambers  should  be  placed  on  suction  and  delivery 
systems,  as  otherwise  there  is  likely  to  be  water-hammer  due  to 
the  sudden  stoppage  of  the  column  of  fluid  in  the  pipes  when  the 
valves  close. 

There  is  no  difficulty  with  the  steam  end  in  using  high  speeds 
provided  the  steam  is  kept  free  from  water.  This  necessitates,  in 
the  case  of  large  pumps,  a  separator  in  the  steam  pipe  just  above 
the  pump,  to  remove  all  water  and  ensure  the  passage  of  none  but 
dry  steam. 

It  is  impossible  to  forewarn  against  all  difficulties  which  may 
arise  in  running  a  steam  pump,  because  it  is  always  "  something 
different"  which  happens,  but  trouble  can  often  be  traced  to  cer- 
tain common  faults.  Defective  valves  in  the  water  end  and 
stoppage  in  the  suction  pipe  are  the  probable  causes  for  irregular 
working  of  a  single  pump.  If  the  pump  slams  on  one  stroke 
and  is  steady  on  the  other,  it  may  be  that  the  discharge  valves  are 
stuck  open  on  one  end  either  by  friction  or  the  lodgement  of  some 
substance  on  the  seat.  Often  a  jar  with  a  hammer  will  remedy 
this  defect,  but  it  is  advisable  to  take  off  the  valve-chamber  cover 
to  find  the  reason  for  the  sticking.  If  the  slamming  is  on  both 
strokes,  it  is  generally  due  to  stoppage  in  the  suction  pipe,  or,  in 
the  case  of  a  pump  ,newly  erected,  it  may  be  that  the  suction  is 
too  small.  If  the  latter  is  the  case,  slowing  down  will  stop  it; 
but  if  there  is  stoppage,  the  pump  will  slam  at  all  speeds.  If  the 


348 


STEAM  PUMPS  89 


suction  is  small,  the  addition  of  a  suction  air  chamber  will  some- 
times  be  beneficial.  Slamming  may  also  be  due  to  a  leak  in  tho 
suction  system  in  either  valves  or  joints,  or  to  a  leak  in  tho  piston 
packing.  Occasionally  the  springs  on  the  inlet  valves  are  too 
strong,  though  this  is  seldom  the  case.  \Vhen  starting  up,  air  in 
the  pump  may  cause  it  to  slam,  the  remedy  being,  of  course,  to 
prime  the  pump  and  suction  pipe  by  pouring  in  \vater,  and  to 
make  sure,  by  opening  the  air  cock  on  top  of  the  water  end,  that 
all  air  is  forced  out  of  the  valve  chamber. 

If  a  pump  sticks  at  the  end  of  the  stroke,  it  is  due  to  friction 
or  improper  valve  setting.  In  the  former  case,  relieving  the 
pressure  on  the  nuts  which  set  up  the  glands  to  the  stuffing  boxes, 
until  there  is  just  enough  pressure  to  prevent  leakage,  will  over- 
come  the  difficulty.  In  the  latter  case  the  valve  motion  should  be 
so  adjusted  as  to  act  earlier  in  the  stroke,  but  it  is  best  to  keep 
the  stroke  of  the  purap  as  long  as  possible  in  order  to  reduce  the 
loss  from  clearance  in  the  steam  cylinder. 

In  starting  up,  particularly  in  cold  weather,  there  will  be 
considerable  condensation  in  the  cylinders,  and  water  will  form 
rapidly.  This  must  be  given  a  chance  to  work  its  way  out  through 
the  drips  which  should  be  left  open  until  the  pump  runs  free  and 
without  sign  of  water  in  the  steam;  the  warming  up  should  be 
done  at  slow  speed. 

If  a  cylinder  oiler  is  used  it  should  be  opened  up  a  sufficient 
time  before  the  pump  is  to  be  started,  so  that  it  may  be  ready  to 
act  immediately  when  the  pump  starts,  as  the  lubrication  is  needed 
when  the  cylinder  is  cold,  even  more  than  at  any  other  time.  It 
is  well  to  have  a  hand-forcing  oil  pump  connected  to  the  steam 
pipe  of  large  pumps  unless  the  feed  of  oil  is  by  a  positively-driven 
pump,  so  that  in  starting  up,  or  in  case  of  emergency,  a  supply  of 
oil  may  be  ensured. 

Before  starting,  the  suction  and  outlet  valves  should  be 
inspected  to  make  sure  that  both  are  open.  If  a  start  is  made 
with  these  closed,  it  is  likely  to  bring  a  pressure  on  the  systems 
which  will  open  the  joints. 

If  the  pump  is  a  large  one  and  is  run  condensing — that  is, 
exhausting  into  a  condenser — the  condenser  should  be  put  in  oper- 
ation first  by  starting  the  flow  of  cooling  water  and  the  air  purnp. 


;49 


90  STEAM  PUMPS 


When  these  are  both  working  well  and  a  good  vacuum  has  been 

established,  the  main  pump  may  be  started. 

In  closing  down,  the  lubricators  may  be  closed  a  little  before 
the  time  to  stop.  The  drips  on  the  steam  cylinder  should  be 
opened  after  stopping  in  order  to  carry  off  the  condensation  from 
any  steam  which  may  remain.  The  drips  on  the  water  cylinder 
need  not  be  opened  unless  there  is  danger  of  freezing,  in  which 
case  the  whole  water  system  should  be  drained.  For  this  purpose 
the  piping  should  all  pitch  toward  the  pump  so  that  the  water 
may  all  be  drawn  off  at  that  point. 

In  the  duplex  type  of  pump,  unless  the  packing  be  adjusted 
with  even  pressure  on  both  sides,  the  side  on  which  the  tighter 
adjustment  is  made  is  liable  to  "  short  stroke ; "  in  fact  this  is 
usually  the  trouble  with  a  pump  which  goes  "  lame  "  on  one  side. 
Jf  the  short  stroking  is  on  one  end  only,  it  is  probably  $ue  to  poor 
setting  of  the  valve-motion  tappets.  Short  stroking  may  also  be 
due  to  tight  packing  on  the  water  piston,  in  which  case  it  can  be 
remedied  by  taking  out  the  packing  and  cutting  off  a  little.  This 
is  likely  to  occur  only  with  pistons  packed  with  square  packing,  as 
those  having  the  cup  leather  packing  or  piston  rings  adjust  their 
own  pressure  between  piston  and  cylinder. 

In  setting  up  a  new  pump,  it  is  important  to  blow  out  all 
pipet3  before  making  the  connections,  in  order  to  make  sure  that 
no  chips  or  dirt  get  into  the  pump.  Unions  should  be  provided 
on  each  pipe  near  the  pump,  so  that,  in  case  of  suspected  stoppage 
of  the  pipe  it  can  be  readily  inspected. 

TESTING. 

The  power  used  by  a  pump  is  usually  so  small  an  item  in  the 
running  expense  of  a  plant,  that  a  test  is  considered  unnecessary; 
and  also  the  steam  exhausted  is  often  used  for  heating  feed  water 
or  for  some  industrial  process.  If  this  is  possible  it  is  usually  an 
economical  way  of  running;  but  in  plants  where  many  pumps  are 
needed,  and  where  heating  feed  water  is  the  only  use  for  the 
exhaust  steam,  more  steam  will  be  available  than  can  be  used  to 
good  advantage;  this  is  especially  true  if  the  main  engines  run  non- 
condensing.  An  economical  pump  is  then  of  great  importance. 

Duty.  In  order  to  determine  the  good  or  bad  performance 
of  a  pump,  it  is  necessary  to  test  it  for  efficiency  and  slip,  the 


350 


STEAM  PUMPS 


test  being  known  as  a  "duty  trial."  The  duty  of  a  pump,  as  the 
term  descended  to  us  from  the  days  of  Watt's  early  pumping 
engines,  was  the  number  of  foot  pounds  of  work  produced 
by  100  pounds  of  coal.  This  is  a  convenient  basis  for  comparison 
of  engines,  but  is  not  accurate,  as  coal  varies  so  much  in  heat 
value;  also  this  method  of  reckoning  involves  the  efficiency  of  the 
boiler  as  well  as  that  of  the  pump.  As  an  attempt  to  eliminate 
the  latter  source  of  error  in  making  comparisons,  a  conventional 
assumption  has  been  made  of  10  pounds  of  steam  evaporated  per 
pound  of  coal;  but  this  is  really  only  the  substitution  of  one 
error  for  another,  for  a  pound  of  steam  when  measured  in  heat 
units  is  by  no  means  a  constant,  and  a  pound  of  coal  seldom  does 
evaporate  10  pounds  of  steam  in  actual  boiler  performance. 
The  more  logical  method  of  comparison  is  by  the  duty  per 
1,000,000  heat  units  furnished  to  the  pump,  a  basis  proposed  by 
a  committee  of  the  American  Society  of  Mechanical  Engineers 
appointed  to  formulate  a  code  for  conducting  such  tests. 

The  duty  of  the  pump  is  found  by  measuring  the  quantity 
of  water  delivered  and  the  height  through  which  it  is  lifted,  or  its 
pressure  equivalent.  The  coal  or  steam  used  must  also  be  meas- 
ured. Then 

^               QIIX  100 
Duty  = 0— 

in  which  Q  =-=  pounds  of  water  delivered, 

11  =  head  against  which  the  pump  works,  both  suction 
and  forcing,  and 

C  =  pounds  of  coal  burned. 
Or  on  the  new  basis.; 

_     Q  II  X  1,000,000 

where  Q  and  H  are  as  before,  and  B  T  U  is  the  heat  units  in  the 
coal  or  steam,  whichever  is  measured. 

An  inaccurate  method  'of  computing  duty  is  sometimes  used, 
which  is  based  on  the  area  of  the  water  piston  or  plunger  and  its 
travel;  but  this  takes  no  account  of  the  slip,  which  may  in  small 
pumps  be  as  much  as  20  per  cent;  hence  it  is  to  be  condemned. 

The  slip  is  found  by  comparing  the  water  actually  delivered 
with  the  total  piston  or  plunger  displacement,  for  the  time  of  the 


351 


STEAM  PUMfS 


test.     The  difference,  measured  as  a  per  cent  of  the  piston  dis. 
placement,  is  the  slip. 

The  \vater  delivered  is  measured  either  by  weighing,  by  the 
use  of  calibrated  tanks,  by  a  weir,  or  by  some  form  of  meter.  One 
of  the  first  two  methods  is  best  for  small  pumps,  and  the  meter  is 
practically  the  only  means  available  for  large  ones  where  the 
delivery  is  into  a  closed  pipe  system.  For  the  weight  or  tank 
method,  the  arrangement  of  Fig.  CO  is  used,  one  tank  being  filled 
while  the  other  is  being  emptied,  through  a  quick  opening  gate 
valve.  If  the  water  is  weighed,  a  certain  amount  as  nearly  as  may 
be  is  run  into  the  tank  and  the  exact  weight  is  caught  after  the 
valve  is  closed  and  the  water  is  flowing  into  the  other  tank.  For 
calibrated  tanks,  the  filling  is  done  nearly  to  a.  set  mark,  at  which 


the  capacity  of  the  tank  is  known,  and  the  exact  level  is  found  by 
dipping  from  the  second  tank.  The  weir  can  be  used  only  where 
the  delivery  is  into  an  open  vessel,  as  the  current  of  water  must  be 
made  to  fiow  over  an  open  notch  as  in  Fig.  70.  The  amount  of 
water  which  passes  this  notch  evidently  depends  on  its  length,  and 
on  the  head  of  water  above  the  sill.  There  is  a  certain  contraction 
as  the  water  enters  the  notch;  but  if  the  edges  are  beveled  to  a 
sharp  edge  up  stream  as  shown,  this  will  be  slight.  The  depth  of 
the  notch  should  be  not  over  i-the  length,  and  is  better  made  con- 
siderably less,  say  from  -J-g-  to  ^.  The  over-fall  below  the  notch 
should  be  at  least  twice  the  depth  of  the  notch.  The  head  of 
water  over  the  sill  should  be  measured  at  a  point  somp  distance 
back  of  the  notch  in  order  to  £et  a  quivet?  even  surface, 


STEAM  PUMPS 


Any  method  of  measuring  the  head  will  answer  which  givea 
it  accurately;  but  a  hook  gauge,  such  as  shown  in  Fig.  71,  will  giv< 
the  best  reoults.  The  reading  of  the  gauge  should  be  taken  when 
set  so  that  the  point  just  breaks  the  surface  as  it  is  brought  up 
from  below,  when  no  water  is  flowing  over  the  notch.  This  givea 
the  height  of  the  sill  from  which  to  calculate.  When  the  water  is 

O 

flowing  from  the  pump,  a  reading  from  the  gauge  is  again  taken 
as  the  point  just  breaks  the  surface.  The  difference  between  the 
two  readings  is  the  head  above  the  sill. 

The  flow,  if  there  were  no  end  contraction,  would  be  Q  =  bvh 
where  Q  is  the  cubic  feet  per  second,  &  the  length,  h  the  head  of 


Fig.  70. 


water  above  the  sill,  and  v  the  velocity  in  feet  per  second.    But  v  » 
2  ff  1  the  same  as  for  falling  bodies,  -  being  used  because  it  is 

the  head  of  center  of  flow.  It  has  been  found  by  experiment  that 
there  is  a  contraction  at  the  ends  and  bottom  of  an  opening,  due 
to  the  in-rush  of  the  water  from  all  sides,  and  that  the  flow  will  be 
about  .62  the  theoretical  amount;  hence 


but  g  is  the  acceleration  due  to  the  force  of  gravity  and  is  equal 
to  32.16;  hence  .62  X  fi  —  3.52  aiid  Q  =  3.52  1$' 


353 


94 


SfEAM  PUMPS 


It  is  found,  however,  that  for  accuracy  the  formula  must  be 
modified  to  take  account  of  the  depth  of  the  water,  and  also  that  the 
coefficient  is  too  large.  Smith  gives,  in  his  Hydraulics,  the  equation 

Q— 


which  is  accurate  for  weirs  for  depth  A,  from  6  inches  to  2  feet 

and  with  length  J,  not  less  than  B/i.     For  large  quantities  of  water 

which  must  be  delivered.  under  pressure, 

the  Venturi  meter  is  the  most  accurate 

means  of  measurement.     This  is  a  pat-  \ 

ented  device  manufactured  by  the  Build- 

ers Iron  Foundry  of  Providence,  K.  I., 

and  registers  the  flow  by  means  of  a 

recording  mechanism  driven  by  clock. 

work.     The  next   best  device   is  some 

form   of  rotary  water  meter,  carefully 

calibrated.     These  will  work  well  with 

cold  water,  but  are  not  to  be  relied  upon 

with  hot  water  as  the  varying  tempera- 

tures affect  the  readings  appreciably. 
For  methods  of  testing  large  pump- 

ing  engines,  the  student  is  referred  to  the 

report  of  the  committee  of  the  American 

Society  of  Mechanical  Engineers,  Yol.  XI 

of  the  Transactions,  which  can  be  obtained 

from  the  Society  in  pamphlet  form  at 

nominal  cost. 

The  following  discussion  will  be  confined  to  small  pumps  : 
For  a  power-driven  pump  it  is  necessary  to  measure  the 

power  supplied.     If  belt-driven,  this  can  best  be  done  by  means 

of  a  transmission  dynamometer,  which  measures  the  pull  on  the 

belt.     Then  this  pull  in  pounds  times  the  speed  of  the  belt  in  feet 

per  minute  equals  the  foot  pounds  per  minute;  and  that  quantity 

divided  by  33,000  gives  the  horse  power.     The  work  performed 

per  minute  will  be  the  weight  of  water  pumped  per  minute  times 

the  distance  through  which  the  water  is  raised  as  indicated  by 

gauges  on  the  suction  and  delivery  pipes  near  the  pump.    These 

heads  can  be  derived  from  the  ordinary  pressure  gauge  readings 


Fig.  71. 


354 


STEAM  PUMPS 


9B 


by  the  table  on  page  9.  The  work  per  minute  divided  by  33,000 
gives  the  delivered  horse  powej-.  For  a  motor-driven  pump  the 
power  applied  can  readily  be  obtained  by  electrical  measurements. 
Measure  the  voltage  and  amperes  of  current  with  the  pump  carry. 

ing  its  load  and  then  Voltage  X  -  ^^  =  Horse  power.    From 

an  efficiency  curve  of  the  motor  as  supplied  by  tho  makers,  or 
obtained  by  a  dynamometer  test  of  the  motor,  get  the  efficiency  at 
the  horse  power  thus  found.  Multiply  the  horse  power  by  the 
efficiency  and  the  product  will  be  the  power  supplied  to  the  pump. 


Fig.  72. 


The  power  delivered  by  it  in  the  form  of  water  pumped  is  found 
by  the  same  method  as  for  the  belted  type. 

For  a  steam-driven  pump  it  is  necessary  to  attach  an  indi- 
cator to  the  steam- end  in  order  to  measure  the  power  supplied  by 
the  steam.  The  indicator  is  connected  as  shown  in  Fig.  72,  to 
register  the  pressure  in  the  cylinder  at  each  point  of  the  stroke. 
The  average  of  these  pressures  is  then  found,  measuring  between 
the  lines  indicating  the  steam  and  exhaust  pressure  as  shown  in 
Fig.  73.  The  sum  of  lines  1,  2,  3,  4,  etc.,  divided  by  the  number 
of  lines  gives  the  average  length,  and  this  multiplied  by  the 
seale  of  the  spring,  or  pounds  pressure  represented  by  an  inch  of 
height,  will  give  the  average  effective  pressure.  The  scale  of  the 
indicator  spring  is  always  found  stamped  on  the  cap  at  one  end 


855 


90 


STEAM  PUMPS 


of  it.  This  average  pressure  multiplied  by  the  area  of  the  piston 
in  square  inches,  by  the  length  of  the  stroke  ia  feet  and  by  the 
number  of  double  strokes  made  per  minute,  gives  the  work  done  per 
minute  in  one  end  of  the  cylinder.  In  the  same  way  pressure 
times  area,  times  length,  times  number  of  strokes,  gives  the  work 
for  the  other  end,  and  the  sum  of  these  amounts  divided  by  33,000 
gives  the  horse  power  developed.  It  should  be  noted  that  there 
is  a  difference  between  the  areas  of  the  two  ends  of  the  piston 
owing  to  the  insertion  of  the  piston  rod  in  one  end. 

Sometimes  the  work  done  in  the  water  cylinder  is  measured 
by  using  the  indicator  in  the  same  way  as  described  for  the  steam 
end.  The  work  done  by  the  water  piston  can,  of  course,  be  found 
by  this  method;  but  there  is  nothing  to  show  whether  the  work  is 
used  in  pumping  water  or  in  slip  and  leakage,  except  that  a  slow 


I      2 


45.6789 


Fig.  73. 


Fig.  74. 


seating  of  the  valves  may  show  in  a  reduced  average  pressure  from 
the  diagram,  as  in  Fig.  74. 

To  test  the  leakage  past  the  piston,  one  cylinder  head  may  be 
removed  and  the  pump  run  single  acting,  the  water  which  passes 
the  piston  into  the  open  end  of  the  cylinder  being  caught  and 
weighed.  This  does  not,  however,  measure  the  leakage  due  to 
faulty  valves  or  seats,  and  the  only  way  this  can  be  found  is  by 
measuring  the  water  actually  pumped. 

The  slip  is  then  found  as  follows:  Multiply  the  area  of  the 
water  piston  by  its  length  of  stroke  and  by  the  number  of  single 
strokes  if  single  acting,  or  double  strokes  if  double  acting — all 
dimensions  being  taken  in  feet — to  get  the  number  of  cubic  feet 
of  water  which  would  be  pumped  per  minute  as  obtained  by  meas- 
urement; subtract  the  water  actually  pumped  and  divide  the 
remainder  by  the  computed  volume  which  should  be  delivered. 


356 


STEAM  PUMPS  97 


The  quotient  expressed  as  a  percentage  is  the  slip.  Slip  is  due  to 
the  leakage  past  the  piston  plunger  and  through  the  valves,  and 
the  amount  varies  with  the  condition  of  packing  and  seats  and 
with  the  promptness  of  valve  closure.  It  can  be  kept  at  a  mini- 
mum by  careful  attention  to  packings,  and  by  running  slowly  and 
steadily  to  allow  the  valves  time  to  seat. 

The  efficiency  of  the  pump  may  be  expressed  according  to 
various  standards.  If  efficiency  as  a  machine,  or  mechanical 
efficiency,  is  desired,  it  is  found  by  dividing  the  horse  power 
utilized  in  pumping  water,  by  that  furnished  to  the  purnp  by  belt, 
motor  or  steam  cylinder.  If  efficiency  of  the  water  end  is  wanted, 
it  is  found  b.y  subtracting  the  percentage  of  slip  from  100.  The 
total  efficiency  is  tha  mechanical  efficiency  multiplied  by  the  pump 
efficiency. 

To  find  the  "  duty  "  the  work  done  in  a  given  time  is  found 
by  one  of  the  processes  already  indicated;  the  heat  furnished  dur- 
ing that  time  is  computed  from  the  coal  burned  and  the  efficiency 
of  the  boiler,  or  better,  by  condensing  the  steam  used  in  a  surface 
condenser,  weighing  it  and  calculating  the  heat  needed  to  evap*- 
orate  that  amount  of  steam,  starting  with  water  at  the  temperature 
of  the  exhaust  steam.  Reduced  to  the  form  of  equations  this 
becomes : 

Foot  pounds  of  work  done. 

Duty  = =L : 

Heat  units  used 

1,000,000 

Foot  pounds  work  =  weight  of  water  multiplied  by  equivalent 
head  overcome.  Heat  units  used  =  Pounds  of  steam  used  X 
(total  heat  at  initial  pressure  minus  the  heat  of  the  liquid  at 
exhaust  pressure). 

The  values  inside  the  parenthesis  must  be  obtained  from 
tables  of  the  properties  of  saturated  steam,  which  are  given  in 
"Boiler  Accessories,"  works  on  the' steam  engine,  or  engineering 
handbooks. 

For  a  power -driven  pump  the  duty  is  found  by  the  formula : 

_  Foot  pounds  of  work  done. 

^        Foot  pounds  furnished  the  pump. 

778"  X   1.000.000 
since  778  foot  pounds  are  equivalent  to  one  heat  unit. 


857 


98 


STEAM  PUMPS 


For  a  motor-driven   pump,  the   foot   pounds   are   equal   to 
average  volts  X  average  amperes  X  time  in  hours  X  2,654.2. 

PUMPING  BY  COMPRESSED  AIR. 

A  system  of  pumping  water  by  compressed  air  was  known 
early  in  the  nineteenth  century,  but  no  practical  working  appa- 
ratus was  devised  until  Dr. 
J.  G.  Pohle  took  up  the 
matter  in  the  early  seventies. 
The  principle  of  operation 
is  shown  in  Fig.  75.  A  dis- 
charge pipe,  D,  is  let  down 
into  the  well  so  that  its  lower 
end  is  deep  below  the  sur. 
face.  Compressed  air  is 
forced  down  through  a 


smaller  air  pipe,  and  is  lib- 
erated inside  the  lower  end 
'ATER  of  the  discharge  pipe  at  a 
*~^FJr J!^.  high  pressure.  The  air  thus 
set  free  forms  a  big  bubble 
the  full  size  of  the  interior 
of  the  discharge  pipe,  dis- 
placing an  equal  volume  of 
water,  and  thus  making  the 
weight  of  the  column  of 
water  and  air  inside  the  pipe 
less  than  an  equal  volume 
of  water  outside  the  pipe. 
The  column  inside  the  pipe 
will  therefore  rise;  and  since 

the  formation  of  air  bubbles  is  continuous  so  long  as  the  com- 
pressed  air  is  supplied,  a  stream  of  slugs  of  water  and  bubbles  of  air 
will  rise  through  the  discharge  pipe  and  flow  out  at  the  upper  end. 
The  air  pressure  used  must  at  first  be  sufficient  to  overcome 
the  head  of  water  in  the  discharge  pipe,  as  well  as  the  friction 
against  the  sides  of  the  pipe.  Also  the  stream  of  water  must 
leave  the  discharge  pipe  with  some  considerable  velocity. 


358 


STEAM  PUMPS  99 


The  pressure  needed  bears  a  ratio  to  the  pressure  due  to  the 
total  head  of  lift  and  immersion  varying  from  0.77  for  compar- 
atively shallow  wells  (100  feet  or  so  deep)  yielding  large  volumes 
of  water,  to  O.G2  for  wells  500  feet  in  depth  and  having  but  a 
small  flow.  Obviously  the  lowest  air  pressure  which  will  do  the 
work  is  the  most  economical,  since  any  excess  of  pressure  is  used 
up  in  producing  unnecessary  velocity  of  discharge  at  the  outlet. 

The  efficiency  increases  as  the  ratio  of  submergence  of  the 
lower  end  of  the  discharge  pipe  below  the  water-level  to  lift  above 
the  water-level  increases.  There  is  much  disagreement  as  to  the 
efficiencies  that  can  be  obtained;  but  tests  seem  to  indicate  that  an 
efficiency  ranging  from  18  per  cent  (for  a  ratio  of  1.5  submerg- 
ence to  lift)  up  to  37  per  cent  (for  a  ratio  of  2.0),  the  efficiency 
being  based  on  the  power  required  to  compress  the  air,  is  as  much 
as  can  be  expected. 

A  great  deal  depends  on  the  proper  proportioning  in  size  of 
air  pipe  to  discharge  pipe,  and  of  submergence  to  lift.  A  cross 
sectional  area  of  water  pipe  0_^  times  that  of  the  air  pipe  has  been 
found  satisfactory;  and  a  submergence  of  twice  the  lift  is  com. 
mon  in  practice,  though  some  tests  seem  to  indicate  that  a  ratio  of 
submergence  to  lift  of  3  to  1  would  give  better  results.  The  ratio 
should  not  in  any  case  be  less  than  1.5  to  1. 

In  this  connection  it  should  be  remembered  that  the  water- 
level  when  pumping  will  always  be  lower  than  when  at  rest,  and 
the  above  ratio  should  be  fixed  for  the  level  under  working  con- 
ditions. 

If  the  air  pipe  be  too  large,  more  air  will  be  furnished  than  is 
needed  and  the  discharge  velocity  will  be  too  great;  if  the  air  pipe 
be  too  small  the  air  bubbles  will  not  expand  sufficiently  to  fill  the 
discharge  pipe  but  will  rise  through  the  water  without  piishing  it 
along  upward. 

A  velocity  not  exceeding  20  feet  per  second  is  recommended 
in  the  air  pipe. 

The  machinery  necessary  for  an  air-lift  system  comprises  the 
following:  an  air  compressor  of  size  sufficient  to  give  the  needed 
air  supply,  a  reservoir  large  enough  to  break  up  the  pulsations 
from  the  compressor  and  steady  the  flow,  gauges  and  valves  for 
regulating  the  pressure,  and  the  necessary  well  piping. 


359 


100 


STEAM  PUMPS 


Ground 

I 

Air  supply 


Ladder 


i 
"     i 

fo   1 
O 

<S 

i 
i 
i 

i 
i — 


CO 


9 


level  disch^rqe 
level 


(flow  to  reservoir) 
Discharge  from  bor'mg 


Steeltubes   !5"di 
"7"  l-nt.  rising  -matin 
21/2  Air  Pipe 
Rest  level 


Approxi-majte  level  of 


Perford-lied  steel  tube 


Air  discKa.rge  pipe 


360 


STEAM  PUMPS 


101 


For  pressures  up  to  60  pounds,  a  single-stage  duplex  com. 
pressor  will  answer;  for  pressures  between  GO  and  300  pounds  a 
two-stage  compressor,  with  an  inter-cooler  between  cylinders,  will 
be  found  economical;  while  for  pressures  above  300  pounds  a 
three-stage  compressor  should  be  used. 


WATER   PIPES 


/AIR   PIPES 


STEAM 


Fig.  77. 

The  supply  of  air  needed  will  vary  with  the  lift,  and  of  course 
with  the  quantity  of  water  handled.  Wm.  II.  Maxwell  gives  the 
following  equation: 

Y==GxL 

20 

where  V  =  cubic  feet  of  free  air  per  minute. 
G  =  cubic  feet  of  water  per  minute. 
L  =  lift  of  water  in  feet. 

The  arrangement  of  air  pipes  and  discharge  pipes  is  largely 
one  of  convenience.  The  least  friction  will  be  produced  by  admit- 
ting  the  air  to  the  bottom  of  the  discharge  pipe  as  shown  in  Fig. 


361 


102  STEAM  PUMPS 


75 ;  but  in  deep  wells  this  is  oftea  inconvenient,  and  the  air  pipe 
is  carried  down  inside  the  water  pipe  as  in  Fig  76. 

For  high  lifts  it  is  sometimes  convenient  to  use  multiple. 
stage  arrangements  as  shown  in  Fig.  77,  the  object  being  to  secure 
sufficient  depth  of  immersion  without  the  expense  of  drilling  a 
very  deep  hole.  Only  one  air  compressor  is  needed,  as  the  pres- 
sure can  be  controlled  by  throttling  the  valves  for  the  lower  stages 
without  serious  loss  of  economy. 

The  advantages  of  the  air-lift  system  are  its  simplicity,  its 
concentration  of  all  machinery  into  one  place  which  can  be  con- 
veniently located,  and  its  ability  to  handle  water  containing  grit, 
stones  or  ashes  without  injury  to  the  machinery.  On  the  other 
hand  the  efficiency  is  low,  and  a  great  depth  of  well  in  proportion 
to  the  lift  is  needed.  The  air-lift  system  is  not  adapted  to  all 
classes  of  service,  but  for  handling  a  number  of  scattered  wells, 
or  a  single  deep  well  in  an  awkward  location,  it  is  simple  and 
effective. 


362 


REVIEW  QUESTIONS. 


PRACTICAL  TEST  QUESTIONS. 

In  the  foregoing  sections  of  this  Cyclopedia 
numerous  illustrative  examples  are  worked  out  in 
detail  in  order  to  show  the  application  of  the  various 
methods  and  principles.  Accompanying  these  are 
examples  for  practice  Avhich  will  aid  the  reader  in 
fixing  the  principles  in  mind. 

In  the  following  pages  are  given  a  large  number 
of  test  questions  and  problems  which  afford  a  valu- 
able means  of  testing  the  reader's  knowledge  of  the 
subjects  treated.  They  will  be  found  excellent  prac- 
tice for  those  preparing  for  College,  Civil  Service,  or 
Engineer's  License.  In  some  cases  numerical  answers 
are  given  as  a  further  aid  in  this  work. 


REVIEW     QUESTIONS 


ON       THE       STTJ5.TECT      Off 


CONSTRUCTION     (>F     P>OIEKRS. 


1.  If  they  are  near  together  how  are  two  flat  parallel  sur- 
faces stayed  ? 

2.  Describe  a  rivet. 

3.  Since  copper  is  such  a  desirable  metal  for  boiler  work 
why  is  it  not  used  more  extensively? 

4.  Why  is  a  large  factor  of  safety  used  for  stays  ? 

5.  Stats  what  you  can  (briefly)  about  the  injuries  done  to 
plates  by  punching  and  the  methods  employed  to  overcome  them. 

G.     Why  are  not  welded  joints  used  more  generally'/ 

7.  In  what  two  ways  are  tubes  fastened  to  the  tube  sheet? 

8.  About   what  is  the  ratio  of  length  to  diameter  of  the 
multitubular  type  of  boiler? 

9.  Explain  riveting  with  countersunk  head. 

10.  Is  the  greatest  tendency  to  rupture  along  the  longitu- 
dinal or  the  circumferential  seams  ? 

11.  Why  is  the  length  of  a  grate  limited? 

12.  Which  is  the  stronger  form  of  riveting,  the  lap  joint  or 
double  butt  joint  (both  with  double  riveting)  ? 

13.  Why  are  the  short  screw  stay  bolts  turned  smooth  in 
the  center  ? 

14.  Why  are  flanged  joints  preferable  to  those  made  with 
cast  iron  angle  irons  ? 

15.  What  is  the  water-leg? 

16.  For  what  qualities  are  boiler  materials  tested? 

17.  What  is  the  principal  advantage  of  pneumatic  calking? 


365 


RE  VIE  TV    QUESTIONS 


TYPES    O 


1.  Why  are  water-tube  boilers  lighter  than  those  of  the  fire- 
tube  type  ? 

2.  In  the  fire-tube  boiler,  are  the   tubes  large  or  small  for 
forced  draft  ?     Why  ? 

3.  Make  a  sketch  of  a  multitubular  boiler  and  locate  the 
important  parts.     Show  by  means  of  arrows  the  path  of  the  hot 
gases. 

XOTE:    The  sketch  should  combine  Figs.  12  and  13. 

4.  Xame  three  boilers  that  have  curved  water  tubes,  are  non- 
sectional,  and  have  a  steam  drum  of  the  cross  type. 

5.  Describe  briefly  the  Stirling  boiler. 

0.  Classify,  under  the  headings  "sectional"  and  "non- 
sectional,"  all  the  water-tube  boilers  described  in  this  Instruction 
Paper. 

7.  Trace  the  changes  that  occurred  in  the  development  of 
the  horizontal  multitubular  boiler  from  the  plain  cylindrical. 

8.  What  is  the  peculiarity  of  Beggs'  Directurn  Boiler  ? 

9.  AVhat  are  the  advantages  of  the  double-ended  return-tube 
boiler  ? 

10.  Trace  the  path  of  the  hot  gases  in  the  Atlas  boiler.     For 
what  purpose  is  the  third  drum  ? 

11.  In  what  way  does  the  Kiclausse    boiler  differ  from  all 
others  here  described  ?     Trace  the  course  of  the  water.     Describe 
the  constri.ction. 

12.  Describe  briefly  the   flue  boilers, — Cornish,  Lancashire, 
and  Galloway.     Identify  each  by  stating  the  peculiarities  in  a  few 
words. 


366 


REVIEW   QUESTIONS 

ON"      THE       S  TJ  B  <J  E  C  X      OF 

BOILER   ACCESSORIES, 


1.  When  are  check  valves  used?     Explain  the  action. 

2.  What  is  the  unit  of  boiler  horse-power? 

3.  What    devices    are    used    to    drain    condensation    from 
steam  pipes  ? 

4.  What  are  the  defects  of  the  lever  safety  valve? 

5.  Why  should  the  feed  supply  be  regulated  so  that  the 
water  level  shall  be  as  nearly  stationary  as  possible  ? 

6.  Describe    the    principle    upon    which    the    injector  or 
inspirator  works. 

7.  Why  is  it  necessary  to  reduce  the  actual  evaporation  to 
an  equivalent  evaporation,  before  comparisons  can  be  made? 

8.  Name  some  methods  for  preventing  smoke. 

9.  Describe  the  two  types  of  feed  water  heaters. 

10.  Of  what   are  fusible    plugs    made?      Where    are  they 
placed  ? 

11.  What  are  the  requisites  of  a  good  boiler  setting  ? 

12.  What  portions  of  a  boiler  should  be  kept  clean? 

13.  What  is  a  good  average  heat  value  for  coal? 

14.  In  building  a  fire  360  pounds  of  wood  were  used.     What 
is  the  coal  equivalent? 

15.  State  some  reasons  why  the  efficiency  of  a  boiler  and 
furnace  is  considerably  less  than  100  per  cent. 

16.  Describe  the  pop  safety  valve, 

17.  What  should  be  the  diameter  of  a  safety  valve  when 


BOILER    ACCESSORIES. 


the  boiler  evaporates  1.346  pounds  of  water  per  second,  if  the  lift 
is  .1  of  an  inch  and  the  pressure  100  pounds  (absolute)  ? 

Ans.     3  inches 

18.  Describe  the  process  of  banking  a  fire. 

19.  What  harm  is  caused  by  the  admission  of  engine  oil  tc 
the  boiler  ? 

20.  In  general,  how  are  boiler  explosions  prevented? 

21.  What  are  the    three    kinds  of   firing? 

22.  Name  and  state  the  objects  of  the  two  kinds  of  boilei 
tests. 

23.  Describe  the  action  of  the  down  draft  furnace. 

24.  Where  is  the  feed  water  generally  introduced? 

25.  Name  some  good  pipe  coverings. 

26.  Why  is  scale  undesirable  ? 

27.  Why  should  the  steam  space  never  be  exposed  to  the 
neat  of  the  fire  ? 

28.  A  lever  safety  valve  is  set  to  blow  off  at  65  pounds. 
The  ball  at  the  end  weighs  110   pounds,  the  lever  weighs  48 
pounds  and  has  its  center  of  gravity  18  inches  from  the  fulcrum. 
The  valve  is  4i  inches  from  the  fulcrum.     The  valve  has  a  diam- 
eter of  4J-  inches  and  with  the  spindle  weighs  14  pounds.     At 
what  distance  from  the  fulcrum  must  the  ball  be  placed  ? 

Ans.     33  J  inches  (nearly) 

29.  Describe  in  detail  the  methods  for  storting  a  fire  in  a 
boiler  furnace,  for  bituminous  coal. 

30.  Why  are"  patches  of  scale  more  harmful  than  a  uniform 
coating  ? 

31.  If  you  were  in  charge  of  a  boiler  and  the  gage  cocks 
gave  no  indication  of  water,  what  would  you  do? 

32.  Describe  briefly  the  two  most  important  kinds  of  coal. 

33.  Show  why  it  is  economical  to  introduce  the  feed  water 
at  a  high  temperature.     What  per  cent,  is  gained  if  the  feed  water 
enters  at  200°  F.  instead  of  60°  F.?     The  pressure  is  110  pounds 


34.  Describe  the  action  and  principle  of  the  Bourdon  gage. 
(  Make  sketch). 

35.  Before  opening  the  drafts,  what  should  a  fireman  do? 


368 


R  E  \r  I  K  W    Q  U  K  S  T  I  O  X  S 


S  T  K  A  M    1»  I J  M 1>  S  . 


1.  Find   the   pressure   per   square  inch  corresponding  to  a 
head  of  187.42  feet. 

2.  Under  what  conditions  should  a  centrifugal  pump  be  used  ? 

3.  Describe  the  rotary  pump. 

4.  If   a   large   quantity   of   water   is  to  be  lifted  a  slight 
amount  (for  instance  20  feet)   is  it  better  to  use  a  direct-acting 
pump  or  a  centrifugal  pump  '. 

5.  How  many  gallons  per  minute  can  be  raised  by  a  purnp 
having  a  water  cylinder  8  inches  in  diameter,  12  inches  stroke,  if 
it  makes  45  double  strokes  per  minute  ?  Assume  Q%  slip. 

6.  What  materials  are  used  for  valve  discs  for  cold  water? 
For  hot  water  ? 

7.  Which  is  the  better  form  of  spring  for  a  valve,  cylindrical 
or  conical  ?     Why  ? 

8.  Under  what  conditions  is  it  better  to  use  a  plunger  pump 
rather  than  the  piston  type  ? 

9.  A  single  cylinder  pump  is  G"xlO".     What  should  be  the 
volume,  diameter  and  height  of  the  air  chamber  on  the  discharge 
pipe  ? 

10.  A  1 2"  xiO"  duplex  makes  52  double  strokes  per  minute. 
What  is  the  piston  speed  in  leet  per  minute  and  what  is  the  dis- 
charge in  gallons  ? 

11.  A  double-acting  pump  is  to  discharge  232  gallons,  per 
minute.     On  account  of  the  pressure  against  which    the   pump 
must  work,  the  water  cylinder  must  be  7  inches  in  diameter.   The 
allowable  number  of  double  strokes  per  minute  is  55.     What  ia 
the  length  of  stroke  \     What  is  the  pistou  speed  \ 


STEAM  PUMPS 


12.  Suppose  a  pump  lias  a  suction  of  14  feet  and  the  loss 
due  to  friction  in  the  piping  is  3  pounds  per  square  inch.     The 
pump  is  a  3"  X  10"  and  the  discharge  is  against  a  head  of  86  feet. 
If  the  pump  makes  40  double  strokes  per  minute,  what  horse  power 
is  required,  allowing  20%  for  friction  ? 

13.  The  head  against  which  a  pump  works  is  122  feet.     If 
the  plunger  is  4  inches  in  diameter  and  the  steam  end  7  inches, 
what  steam  pressure  must  be  used?    Consider  the  plunger  friction 
to  be  75  pounds. 

14.  A  boiler-feed  pump  works  against  a  pressure  of  145 
pounds.     It  draws  water  from  a  tank  located  so  that  the  lift  is  16 
feet.     If  the  steam  pressure  at  the  pump  is  130  pounds  and  steam 
cylinder  is  8  inches  in  diameter,  what  is  the  diameter  of  the  plun- 
ger ?     (a)   Make  LD  allowance  for  friction,     (b)    Assume  friction 
to  be  15%. 

15.  Describe  the  setting  of  the  valves  of  a  duplex  pump. 

16.  Describe  the  valve  motion  of  a  duplex  pump. 

17.  Draw  a  diagram  and  locate  the  high-pressure  cylinder, 
the  low-pressure  cylinder,  the  pistons,  the  piston  rod,  water  cylin- 
der plunger,  and  air  chamber  of  a  tandem  compound  pump. 

18.  What  mear-s  are  used  for  connecting  the  shaft  of  a  gag 
or  steam  engine  to  a  triplex  pump  ? 

10.     How  is  steam  cushion  obtained  in  a  pump  ? 

20.  Why  are  laps  added  to  steam  valves  ? 

21.  What  should  be  the  maximum  lift  for  a  disc  valve  ? 

22.  Explain  with  sketch  the  action  of  the  combined  forcing 
and  lifting  pump  (double  acting). 

23.  Describe   the    usual    lost-motion    device    for   a  duplex 
pump.     Why  is  it  used  ? 

24.  Where  should  the  check  valve  of  a  suction  end  be  placed? 

25.  What  kind  of  packing  is  commonly  used  in  the  water- 
end  stuffing  box  ? 

26.  If  a  pump  slams  on  one  stroke  but  not  on  the  other, 
what  is  the  probable  cause  ? 

27.  Give  method  of  procedure  in  starting  a  compound  con- 
densing  pump. 

28.  What  is  the  most  common  cause  of  short  stroke  on  one 
side  of  a  duplex  pump  ? 


370 


INDEX 


The  page  numbers  of  I/its 

volume 

will  be  found  nt  the  bottom  of  the 

pages;  the  numbers 

at  the 

top  refer  only  to  the  section. 

Page 

Page 

A 

Boiler  attachments 

69 

Adamson  furnace  flue 

41 

Boiler  classification 

71 

Air  pumps 

316 

according  to  forms  of  construct  ioi 

Angle  valve 

179 

early  forms 

72 

"Ashton"  safety-valve 

185 

fire-tube 

SO 

Atlas  water-tube  boiler 

121 

flue 

75 

B 

water-.tube 

108 

Babcock  and  Wilcox  water-tube  boiler 

113 

according  to  use 

Ball  valves 

290 

locomotive 

98 

Barrel  calorimeter 

209 

marine 

89 

Belpaire  boiler 

102 

stationary 

-•2 

Blake  valve 

327 

Boiler  construction 

11-67 

Blow-off  pipe 

69 

brackets 

63 

Boiler  accessories                                       143-260 

calking 

42 

blow-out  apparatus 

187 

chimneys 

64 

calorimeters 

208 

design 

44 

circulating  apparatus 

198 

dimensions 

50 

evaporators 

199 

end  plate 

53 

feed  apparatus 

190 

furnace  Hues 

41 

feed-water  heaters 

200 

grate  area 

45 

fuel  economizers 

159 

heating  surface 

50 

furnaces 

149 

horse  power 

44 

fusible  plugs 

162 

manholes 

63 

gauges 

171 

materials  used  in 

11 

hollow  arch 

157 

plates  and  joints,  arrangement  of 

26 

injectors 

196 

rivets  and  riveting 

20 

manholes  and  handholes 

170 

sections 

60 

pumps 

195 

staying 

32 

return  traps 

208 

tubes 

39.    47 

settings 

143 

uptake 

62 

steam  separators 

203 

water  level 

53 

steam  traps 

206 

Boiler  corrosion  and  incrustation 

223 

supports 

148 

Boiler  coverings 

220 

tube-cleaners 

168 

Boiler  design 

44 

tube-stoppers 

168 

Boiler  dimensions 

50 

valves 

178 

Boiler  explosions 

230 

Note.  —  For  piti/c  numbers  see  foot  of  pages. 

371 


2 

INDEX 

Page 

Page 

Boiler  explosions 

Combined-condenser  pump 

315 

causes  of 

•232 

Competition  valve 

179 

investigation  of 

235 

Compound  pumps 

331 

prevention  of 

236 

Construction  of  boilers 

11-67 

Boiler  horse-power 

44,   221 

Copper  for  boiler  construction 

12 

Boiler  materials 

Cornish  boiler 

76 

brass 

12 

Corrosion 

223 

cast  iron 

11 

external 

223 

copper 

12 

internal 

224 

steel 

12 

Corrugated  furnace  flue 

42 

strength  of 

15 

Crowfoot  stay 

35 

tensile  strength  of 

15 

Cylindrical  boiler 

74 

testing  of  • 

13 

D 

wrought  iron 

12 

Deane  of  Holyoke  pump  valve 

325 

Boiler  setting 

143 

Diagonal  stays 

35 

Boiler  shop  equipment 

17 

Dial  gauge 

171 

Boiler  stays 

33 

Differential  steam  trap 

207 

crowfoot 

35 

Directurn  boiler 

107 

diagonal 

35 

Donkey  pump 

191 

gusset 

34 

Double  beat  valves 

290 

Boiler  supports 

148 

Double  riveting 

23 

Boiler  tubes 

39,   47,   61 

Double-tube  boiler,  definition  of 

70 

Boilers 

Down-draft  furnaces 

157 

care  of 

257 

Draft-gauge 

164 

strength  of 

53 

Drafts 

types  of 

69-141 

forced 

165 

Brass 

12 

closed  ash-pit 

165 

Bucket  trap 

206 

closed  stoke-hold 

165 

Butt  riveting 

23 

induced  draft 

166 

C 

natural 

164 

Cahall  water-tube  boiler 

135 

Drilled  boiler  plates 

18 

Calking  boiler  joints 

42 

Duplex  pump 

309 

Calorimeters 

208 

E 

barrel 

209 

"Eames  Differential"  draft-gauge 

164 

separator 

212 

Ellis  and  Eaves  system  of  forced  draft 

166 

throttling 

213 

Evaporators 

199 

Cameron  pump  valve 

323 

Externally-fired  boiler,  definition  of 

70 

Care  of  boilers,  rules  for 

257 

F 

Cast  iron 

11 

Feed  pump 

69 

Centrifugal  pumps 

276 

Feed-water  heaters 

200 

Chain  riveting 

23 

Fire-box  boilers 

Check-  valves 

180 

definition  of 

70 

Chimneys 

64 

Maiming 

87 

Clearance 

296 

upright 

85 

Cochraue  feed-water  heater 

201 

Fire  pumps 

304 

Cochraue  steam  separator 

205 

Fire-tube  boiler,  definition  of 

70 

Cochranc  vertical  boiler 

104 

Firing  for  boilers 

253 

Note.  —  Fur  page  numbers  see  foot 

of  pagec. 

372 


Flanging  iron  and  steel  plates 
Flat  seat  valve 
Flexible  valve 
Float  trap 
Flue  boilers 
Cornish 
Galloway 
Lancashire 
single-flue 
Forced  draft 

Ellis  and  Eaves  system 
Howden  system 
Forcing  pumps 
"Foster"  reducing  valve 
Fuel  economizers 
Fuel  for  steam  production 
Furnace 
bridge 

combustion  in 
door  of 
down-draft 
grate 

hollow  arch 
mechanical  stokers 
prevention  of  smoke 
special 

Furnace  flues 
Fusible  plugs 

G 

Galloway  boiler 
Gate  valve 
Gauge  cocks 
Gauge-glasses 
Gauges 

steam  and  vacuum 
water 

Globe  valve 
Grate  area  for  boilers 
Gusset  stays 

II 

"Hancock"  inspirator 
Harrison  water-tube  boiler 
Haystack  boiler 
Hazelton  water-tube  boiler 
Heating  surface  of  boiler 
Heine  water-tube  boiler 
Hinged  valves 
Note. — For  payc  numbers  see  foot 


INDEX 

3 

Page 

Page 

25 

"Holt"  valve 

187 

289 

Horse-power  of  boilers 

221 

286 

Howden  system  of  forced  draft 

166 

206 

Hydraulic  ram 

OftO 

75 

Hydraulic  riveting 

—  uo 
21 

76 

Hydrotrophe 

85 

79 

I 

77 
SO 

Incrustation 

226 

Injectors 

196 

166 

Inspirator 

196 

166 

Internally-fired  boiler,  definition  of 

70 

Iron  and  steel  plates,  flanging 

187 

J 

159 

Jet  pump 

271 

236 

Joints  for  boiler  shells 

149 

riveted 

24 

154 

•    welded 

25 

150 

K 

151 

"Klinger  Patent"  water  gauge-glass 

177 

157 

Knowles  pump  valve 

322 

151 

157 

L 

161 

Lancashire  boiler 

77 

155 

Leather  valves 

288 

154 

Lentz  boiler 

103 

41,   60 

Lever  safety-valve 

182 

69 

Lifting  pumps 

279 

Locomotive  boilers 

Belpaire 

102 

70 

Lentz 

103 

180 

Wootten 

102 

69 

M 

175 

Machine  riveting 

21 

Manholes 

63,    170 

171 

Manning  boiler 

87 

174 

Marine  boilers 

178 
45 

double-ended 

93 

earliest  forms 

90 

34 

return-tube 

89,   95 

through-tube 

96 

197 

water-tube 

10S 

140 

"Mason"  valve 

187 

72 

Mechanical  stokers 

161 

139 

Milne  water-tube  boiler 

13H 

50 

Mitre  valve 

280 

119 

Mosher  water-tube  boiler 

123 

288 

Motor-driven  pump 

313 

f  panes. 


873 


4 

INDEX 

Page 

Page 

N 

Riveting 

Niclausse  water-tube  boiler 

129 

hydraulic 

21 

Non-sectional  boiler,  definition  of 

70 

machine 

21 

P 

Rivets 

20 

Pipes 

215 

dimensions  of 

20 

coverings  for 

218 

testing 

21 

lagging 

217 

types  of 

21 

Piston,  size  of 

298 

Robb-Mumford  boiler 

105 

Plates  and  joints  of  boilers,  arrangement; 

5 

Rocking  grates 

153 

of 

26 

Root  water-tube  boiler 

115 

Pop  safety-valve 

184 

Rotary  pumps 

273 

Poppet  valve 

288 

S 

Pressure  gauge 
Priming 

69 
203 

Safety-valves 

69,   181 

Pulsometer 

285 

lever 

182 

Pump  duty 
Pump  efficiency 
Pump  slip 
Pump  valves 
ball 

357 
357 
356 

286 
290 

Pop 
Sectional  boiler,  definition  of 
Separator  calorimeter 
Setting  for  a  stationary  boiler 
Shapley  boiler 

184 
70 
212 
143 
104 

double  beat 

290 

Single  pump 

308 

flat 

289 

Single-tube  boiler,  definition  of 

70 

flexible 

286 

Slip 

351 

hinged 

288 

Smoke,  prevention  of 

155 

leather 

288 

Split  draft 

73 

mitre 

289 

"Star  Marine"  pop  safety-valve 

186 

poppet 

288 

Stationary  boilers 

Pumping  by  compressed  air 
Pumps 

358 

cylindrical 
early  forms 

74 
72 

air 

316 

fire-box 

85,   103 

centrifugal  pumps 
combined-condenser 

276 
315 

flue 
multitubular 

80 

compound 

331 

water-tube 

108 

Davidson 

328 

Staying  boiler  shell 

32,   53 

duplex                                                309, 

330 

Steam  boiler  trials 

243-253 

for  feeding  boilers 

195 

Steam-driven  pump 

313 

forcing 

Og9 

Steam  jets 

167 

hydraulic  ram 

268 

Steam  pipe 

69 

jet 

271 

Steam  pumps 

263-362 

lifting 

279 

arrangement  of  parts 

297 

rotary 

273 

care  of 

346 

single 

308 

design  and  construction 

291 

triplex 

309 

air  chamber 

295 

clearance 

296 

R 

cylinder 

292 

Reducing  valvos 

186 

frame 

297 

Return  traps 

208 

piston  rod 

293 

Riveted  joints                                        22,   24 

,   56 

ports 

296 

Note. — For  page  numbers  see  foot  of  pages. 


374 


INDEX 

5 

Page 

Page 

Steam  pumps 

Table 

design  and  construction 

fire  pumps,  dimensions  and  capaci- 

stuffing-box 

296 

ties  of 

306 

valves 

292 

forced  draft 

46 

water  end  of  pump 

293 

friction  of  water  in  pipes 

345 

driving,  methods  of 

310 

gases,  evaporative  power  of 

242 

earliest  example 

265 

heat  loss  in  bare  pipes 
heat  loss  in  pipes,  variation  of.  with 

218 

erection  and  piping 

340 

pressure 

218 

kinds  of 

271 

lap  joints 

59 

setting  valves  on 

336 

lap  welded  boiler  tubes 

48 

testing 

350 

piston  rod  data 

293 

types  of    s 

307 

pressure  heads  of  steam  pumps 

26!l 

valves  for 

286 

pump  capacity  in  gallons  per  in  in.  at 

Steam  separators 

203 

60  double  strokes  permin. 

:;oo 

Cochrane 

205 

radiation  of  heat,  various  preventu- 

Stratton 

205 

tivesof 

21  !l 

Steam  spare  of  boiler 

49 

relation  of  efficiencies  and  ratio  of 

Steam  traps 

200 

lifting  to  forcing   heads 

270 

bucket 

206 

rivet  dimensions 

20 

differential 

207 

riveted   joints,   relative  strengths  of 

24 

float 

206 

saturated  steam,  table  of  properties 

Steam  valves 

320 

of 

260 

"B"  type 

321 

slip,  approximate  values  of 

301 

Blake 

327 

suction  and  delivery  pipes,  sixes  of 

344 

Tensile  strength  of  boiler  materials 

15 

Cameron 

323 

"D"  type 

321 

Thornycroft-Marshall   water-tube  boiler 

127 

Deane  of  Hoi  yoke 

Throttling  calorimeter 

213 

Knowles 

3o2 

Triplex  pump 

300 

Steel  for  boiler-shell  work 

JO 

Try-cocks 

175 

Stirling  water-tube  boiler 

135 

Tube-cleaners 

168 

Stratton  steam  separator 
Strength  of  boilers 
Supports  for  boilers 

205 
53 
14S 

Tube  space  of  boiler 
Tube-stoppers 
Tubes  for  boilers                                    39,   47 

4» 

16S 
,    61 

Types  of  boilers                                             69-141 

T 

u 

Table 

Upright  boilers 

85 

barometer  readings 

204 

V 

chimney  data 

65 

Valve  area 

301 

chimney  draft- 

46 

Valve  setting  on  pumps 

336 

coals,  analysis  and  heat   value  of 

Valves 

various 

237 

angle 

170 

compound-pump  details,  proportions 

ball 

290 

of 

336 

check 

ISO 

evaporation,  factors  of 

222 

double  beat 

2!>0 

evaporative  test  of  boiler  trial,  data 

flat  seat 

L'S't 

and  results  of 

252 

flexible 

2.X6 

Note.  —  For  pane  numbers  see  foot  n/'  panes. 

375 


INDEX 


•Valves 
gate 
globe 
hinged 
leather 
materials  for 
mitre 
poppet 
reducing 
safety 


W 


Page 

ISO 
178 
288 
2S8 
181 
289 
288 

isr, 

181 


Wagon  boiler  73 

Water  gauges  174 

Water  space  of  boiler  49 
Note. — For  page  numbers  .ire  [nut  uf  par/es. 


Water-tube  boilers 

definition  of 

horizontal 

peculiar  forms 

vertical 
Welded  joints 
Wheel  draft 

Wickes  water-tube  boiler 
Wootten  boiler 
Worthington  steam  pump 
Worthington  water-tube  boiler 
Wrought  iron  for  boiler  plates 

Z 
Zigzag  riveting 


Page 
108 

70 
113 
139 
132 

25 

73 
132 
102 
195 
117 

12 


376 


